Organic Compound, Light-Emitting Element, Light-Emitting Device, Electronic Device, and Lighting Device

ABSTRACT

A novel organic compound having a high hole-transport property is provided. A long-lifetime light-emitting element is provided. An organic compound represented by General Formula (G0) is provided. In General Formula (G0), Ar 1  represents a substituted or unsubstituted naphthyl group, Ar 2  represents a substituted or unsubstituted carbazolyl group, Ar 3  represents a substituted or unsubstituted fluorenyl group or a substituted or unsubstituted spirofluorenyl group, and α 1  and α 2  each independently represent a substituted or unsubstituted phenylene group or a substituted or unsubstituted biphenyldiyl group.

This application is a continuation of copending U.S. application Ser.No. 13/957,023, filed on Aug. 1, 2013 which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an organic compound, a light-emittingelement, a light-emitting device, an electronic device, and a lightingdevice.

2. Description of the Related Art

In recent years, research and development have been extensivelyconducted on light-emitting elements using electroluminescence (EL)(also referred to as EL element). In a basic structure of an EL element,a layer containing a light-emitting substance is provided between a pairof electrodes. By applying voltage to this element, light emission fromthe light-emitting substance can be obtained.

An EL element is a self-luminous element and thus has advantages over aliquid crystal display element, such as high visibility of the pixelsand no need of backlight, and is considered to be suitable as a flatpanel display element. Another major advantage of such an EL element isthat it can be manufactured to be thin and lightweight. Besides, the ELelement has an advantage of quite fast response speed.

Since an EL element can be formed in a film form, planar light emissioncan be obtained; thus, a large-area element can be easily formed. Thisfeature is difficult to obtain with point light sources typified byincandescent lamps and LEDs or linear light sources typified byfluorescent lamps. Thus, the light-emitting element also has greatpotential as a planar light source applicable to a lighting device andthe like.

EL elements can be broadly classified according to whether alight-emitting substance is an organic compound or an inorganiccompound. In the case of an organic EL element in which a layercontaining an organic compound used as a light-emitting substance isprovided between a pair of electrodes, by applying a voltage to thelight-emitting element, electrons from a cathode and holes from an anodeare injected into the layer containing the organic compound and thus acurrent flows. The injected electrons and holes then lead the organiccompound to its excited state, so that light emission is obtained fromthe excited organic compound.

The excited state formed by an organic compound can be a singlet excitedstate or a triplet excited state. Light emission from the singletexcited state (S*) is called fluorescence, and emission from the tripletexcited state (T*) is called phosphorescence.

In improving element characteristics of the light-emitting element,there are many problems which depend on substances used for thelight-emitting element. Therefore, improvement in an element structure,development of a substance, and the like have been carried out in orderto solve the problems. For example, Patent Document 1 discloses acarbazole derivative having a high hole-transport property as a materialthat can be used for forming a light-emitting element with high emissionefficiency.

REFERENCE

[Patent Document 1] Japanese Published Patent Application No.2009-298767

SUMMARY OF THE INVENTION

The development of organic EL elements has room for improvement inemission efficiency, reliability, cost, and the like. More excellentsubstances are desired to be developed.

An object of one embodiment of the present invention is to provide anovel organic compound having a high hole-transport property.

Another object of one embodiment of the present invention is to providea light-emitting element having a long lifetime.

Another object of one embodiment of the present invention is to providea light-emitting device, an electronic device, and a lighting deviceeach having high reliability by using the above light-emitting element.

The organic compound of one embodiment of the present invention is atertiary amine in which a substituent including a fluorene skeleton or aspirofluorene skeleton, a substituent including a naphthalene skeleton,and a substituent including a carbazole skeleton are directly bonded toa nitrogen atom. The organic compound of one embodiment of the presentinvention has a high hole-transport property.

Specifically, one embodiment of the present invention is an organiccompound represented by General Formula (G0).

In General Formula (G0), Ar¹ represents a naphthyl group; Ar² representsa carbazolyl group; Ar³ represents a fluorenyl group or a spirofluorenylgroup; and α¹ and α² each independently represent a phenylene group or abiphenyldiyl group. The naphthyl group, the carbazolyl group, thefluorenyl group, the spirofluorenyl group, the phenylene group, and thebiphenyldiyl group are each independently unsubstituted or substituted.In the case where any of the groups has a substituent, the substituentis an alkyl group having 1 to 10 carbon atoms or an aryl group having 6to 25 carbon atoms.

Another embodiment of the present invention is an organic compoundrepresented by General Formula (G1).

In General Formula (G1), Ar¹ represents a naphthyl group; Ar³ representsa fluorenyl group or a spirofluorenyl group; Ar⁴ represents an arylgroup having 6 to 25 carbon atoms; α¹ represents a phenylene group or abiphenyldiyl group; and R¹¹ to R¹⁷ and R²¹ to R²⁴ each independentlyrepresent hydrogen, an alkyl group having 1 to 10 carbon atoms, or anaryl group having 6 to 25 carbon atoms. The naphthyl group, thefluorenyl group, the spirofluorenyl group, the phenylene group, and thebiphenyldiyl group are each independently unsubstituted or substituted.In the case where any of the groups has a substituent, the substituentis an alkyl group having 1 to 10 carbon atoms or an aryl group having 6to 25 carbon atoms.

Another embodiment of the present invention is an organic compoundrepresented by General Formula (G2).

In General Formula (G2), Ar¹ represents a naphthyl group; Ar³ representsa fluorenyl group or a spirofluorenyl group; α¹ represents a phenylenegroup or a biphenyldiyl group; R¹¹ to R¹⁷ and R²¹ to R²⁴ eachindependently represent hydrogen, an alkyl group having 1 to 10 carbonatoms, or an aryl group having 6 to 25 carbon atoms; and R³¹ to R³⁵ eachindependently represent hydrogen or an alkyl group having 1 to 10 carbonatoms. The naphthyl group, the fluorenyl group, the spirofluorenylgroup, the phenylene group, and the biphenyldiyl group are eachindependently unsubstituted or substituted. In the case where any of thegroups has a substituent, the substituent is an alkyl group having 1 to10 carbon atoms or an aryl group having 6 to 25 carbon atoms.

Another embodiment of the present invention is an organic compoundrepresented by General Formula (G3).

In General Formula (G3), Ar³ represents a fluorenyl group or aspirofluorenyl group; R¹¹ to R¹⁷, R²¹ to R²⁴, R⁴¹ to R⁴⁷, and R⁵¹ to R⁵⁴each independently represent hydrogen, an alkyl group having 1 to 10carbon atoms, or an aryl group having 6 to 25 carbon atoms; and R³¹ toR³⁵ each independently represent hydrogen or an alkyl group having 1 to10 carbon atoms. The fluorenyl group or the spirofluorenyl group isunsubstituted or substituted. In the case where the fluorenyl group orthe spirofluorenyl group has a substituent, the substituent is an alkylgroup having 1 to 10 carbon atoms or an aryl group having 6 to 25 carbonatoms.

Another embodiment of the present invention is a light-emitting elementincluding any of the above-described organic compounds between a pair ofelectrodes.

Another embodiment of the present invention is a light-emitting elementincluding a light-emitting layer between a pair of electrodes, and thelight-emitting layer contains any of the above-described organiccompounds and a light-emitting substance. Another embodiment of thepresent invention is a light-emitting element including a light-emittinglayer between a pair of electrodes, and the light-emitting layercontains a first organic compound, a second organic compound, and alight-emitting substance. The first organic compound is any of theabove-described organic compounds, and the second organic compound is anorganic compound having an electron-transport property. In particular,the combination of the first organic compound and the second organiccompound preferably forms an exciplex, in which case emission efficiencyof the light-emitting element can be enhanced.

Another embodiment of the present invention is a light-emitting elementincluding, between a pair of electrodes, a light-emitting layercontaining a light-emitting substance and a hole-transport layer that isin contact with the light-emitting layer.

The hole-transport layer contains any of the above-described organiccompounds.

Another embodiment of the present invention is a light-emitting elementincluding, between a pair of electrodes, a light-emitting layer and ahole-transport layer that is in contact with the light-emitting layer.The light-emitting layer contains a light-emitting substance and any ofthe above-described organic compounds. The hole-transport layer containsthe organic compound of one embodiment of the present invention.

Another embodiment of the present invention is a light-emitting deviceincluding any of the above-described light-emitting elements in alight-emitting portion. Another embodiment of the present invention isan electronic device including the light-emitting device in a displayportion. Another embodiment of the present invention is a lightingdevice including the light-emitting device in a light-emitting portion.

The light-emitting element including the organic compound of oneembodiment of the present invention has a long lifetime; thus, a highlyreliable light-emitting device can be achieved. Similarly, a highlyreliable electronic device and a highly reliable lighting device can beachieved by application of one embodiment of the present invention.

The light-emitting device in this specification includes an imagedisplay device that uses a light-emitting element. The category of thelight-emitting device in this specification includes a module in which alight-emitting element is provided with a connector such as ananisotropic conductive film or a TCP (tape carrier package); a module inwhich a printed wiring board is provided at the end of a TCP; and amodule in which an IC (integrated circuit) is directly mounted on alight-emitting element by a COG (chip on glass) method. In addition, alight-emitting device that is used in lighting equipment and the likeare also included.

The above-described organic compounds of one embodiment of the presentinvention has a high hole-transport property. With the use of theorganic compound of one embodiment of the present invention, alight-emitting element having a long lifetime can be achieved.Furthermore, by application of one embodiment of the present invention,a highly reliable light-emitting device, a highly reliable electronicdevice, and a highly reliable lighting device can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1F each illustrate an example of a light-emitting element ofone embodiment of the present invention.

FIG. 2 illustrates an example of a light-emitting element of oneembodiment of the present invention.

FIGS. 3A and 3B illustrate an example of a light-emitting device of oneembodiment of the present invention.

FIGS. 4A and 4B illustrate an example of a light-emitting device of oneembodiment of the present invention.

FIGS. 5A to 5E each illustrate an electronic device of one embodiment ofthe present invention.

FIGS. 6A and 6B illustrate examples of lighting devices of oneembodiment of the present invention.

FIGS. 7A and 7B are ¹H NMR charts of9,9-dimethyl-N-[4-(1-naphthyl)phenyl]-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9H-fluoren-2-amine(abbreviation: PCBNBF).

FIGS. 8A and 8B show an absorption spectrum and an emission spectrum ofPCBNBF in a toluene solution of PCBNBF.

FIGS. 9A and 9B show an absorption spectrum and an emission spectrum ofa thin film of PCBNBF.

FIGS. 10A and 10B are ¹H NMR charts ofN-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-N-[4-(1-naphthyl)phenyl]-9,9′-spirobi[9H-fluoren]-2-amine(abbreviation: PCBNBSF).

FIGS. 11A and 11B show an absorption spectrum and an emission spectrumof a toluene solution of PCBNBSF.

FIGS. 12A and 12B show an absorption spectrum and an emission spectrumof a thin film of PCBNBSF.

FIG. 13 illustrates a light-emitting element of Example.

FIG. 14 shows luminance-current efficiency characteristics oflight-emitting elements of Example 3.

FIG. 15 shows voltage-luminance characteristics of the light-emittingelements of Example 3.

FIG. 16 shows luminance-external quantum efficiency characteristics ofthe light-emitting elements of Example 3.

FIG. 17 shows the results of reliability tests of the light-emittingelements of Example 3.

FIG. 18 shows luminance-current efficiency characteristics oflight-emitting elements of Example 4.

FIG. 19 shows voltage-luminance characteristics of the light-emittingelements of Example 4.

FIG. 20 shows luminance-external quantum efficiency characteristics ofthe light-emitting elements of Example 4.

FIGS. 21A and 21B show the results of reliability tests of thelight-emitting elements of Example 4.

FIGS. 22A and 22B show the results of LC/MS analysis of PCBNBF.

FIGS. 23A and 23B show the results of LC/MS analysis of PCBNBSF.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be described with reference tothe drawings. Note that the present invention is not limited to thefollowing description, and it is easily understood by those skilled inthe art that various changes for embodiments and details can be madewithout departing from the spirit and scope of the invention. Therefore,the present invention should not be construed as being limited to thedescription in the following embodiments. Note that in the structures ofthe invention described below, the same portions or portions havingsimilar functions are denoted by the same reference numerals indifferent drawings, and description of such portions is not repeated.

Embodiment 1

In this embodiment, an organic compound of one embodiment of the presentinvention will be described.

One embodiment of the present invention is a tertiary amine in which asubstituent including a fluorene skeleton or a spirofluorene skeleton, asubstituent including a naphthalene skeleton, and a substituentincluding a carbazole skeleton are directly bonded to a nitrogen atom.The organic compound of one embodiment of the present invention has ahigh hole-transport property. With the use of the organic compound, alight-emitting element with a long lifetime can be achieved.

Specifically, one embodiment of the present invention is an organiccompound represented by General Formula (G0).

In General Formula (G0), Ar¹ represents a naphthyl group; Ar² representsa carbazolyl group; Ar³ represents a fluorenyl group or a spirofluorenylgroup; and α¹ and α² each independently represent a phenylene group or abiphenyldiyl group. The naphthyl group, the carbazolyl group, thefluorenyl group, the spirofluorenyl group, the phenylene group, and thebiphenyldiyl group are each independently unsubstituted or substituted.In the case where any of the groups has a substituent, the substituentis an alkyl group having 1 to 10 carbon atoms or an aryl group having 6to 25 carbon atoms.

Specific examples of Ar² in General Formula (G0) include substituentsrepresented by Structural Formulae (1-1) to (1-27).

Another embodiment of the present invention is an organic compoundrepresented by General Formula (G1). The range of choices for asynthesis method of the organic compound represented by General Formula(G1) is wide, which is preferable because purification of a material anda reduction in cost of the organic compound can be easily achieved.

In General Formula (G1), Ar¹ represents a naphthyl group; Ar³ representsa fluorenyl group or a spirofluorenyl group; Ar⁴ represents an arylgroup having 6 to 25 carbon atoms; α¹ represents a phenylene group or abiphenyldiyl group; and R¹¹ to R¹⁷ and R²¹ to R²⁴ each independentlyrepresent hydrogen, an alkyl group having 1 to 10 carbon atoms, or anaryl group having 6 to 25 carbon atoms. The naphthyl group, thefluorenyl group, the spirofluorenyl group, the phenylene group, and thebiphenyldiyl group are each independently unsubstituted or substituted.In the case where any of the groups has a substituent, the substituentis an alkyl group having 1 to 10 carbon atoms or an aryl group having 6to 25 carbon atoms.

In General Formula (G1), Ar⁴ is preferably a phenyl group, in which casethe thermophysical property of the organic compound is improved incomparison with the case where Ar⁴ is an alkyl group, so that along-lifetime light-emitting element can be fabricated. Thus, anotherembodiment of the present invention is an organic compound representedby General Formula (G2).

In General Formula (G2), Ar¹ represents a naphthyl group; Ar³ representsa fluorenyl group or a spirofluorenyl group; α¹ represents a phenylenegroup or a biphenyldiyl group; R¹¹ to R¹⁷ and R²¹ to R²⁴ eachindependently represent hydrogen, an alkyl group having 1 to 10 carbonatoms, or an aryl group having 6 to 25 carbon atoms; and R³¹ to R³⁵ eachindependently represent hydrogen or an alkyl group having 1 to 10 carbonatoms. The naphthyl group, the fluorenyl group, the spirofluorenylgroup, the phenylene group, and the biphenyldiyl group are eachindependently unsubstituted or substituted. In the case where any of thegroups has a substituent, the substituent is an alkyl group having 1 to10 carbon atoms or an aryl group having 6 to 25 carbon atoms.

Specific examples of Ar¹ in General Formulae (G0) to (G2) includesubstituents represented by Structural Formulae (2-1) to (2-3).

Specific examples of α¹ in General Formulae (G0) to (G2) and α² inGeneral Formula (G0) include substituents represented by StructuralFormulae (3-1) to (3-12).

Another embodiment of the present invention is an organic compoundrepresented by General Formula (G3). The organic compound represented byGeneral Formula (G3) is preferred because the synthetic cost can be low.

In General Formula (G3), Ar³ represents a fluorenyl group or aspirofluorenyl group; R¹¹ to R¹⁷, R²¹ to R²⁴, R⁴¹ to R⁴⁷, and R⁵¹ to R⁵⁴each independently represent hydrogen, an alkyl group having 1 to 10carbon atoms, or an aryl group having 6 to 25 carbon atoms; and R³¹ toR³⁵ each independently represent hydrogen or an alkyl group having 1 to10 carbon atoms. The fluorenyl group or the spirofluorenyl group isunsubstituted or substituted. In the case where the fluorenyl group orthe spirofluorenyl group has a substituent, the substituent is an alkylgroup having 1 to 10 carbon atoms or an aryl group having 6 to 25 carbonatoms.

In each of the above General Formulae, specific examples of Ar³ includesubstituents represented by Structural formulae (4-1) to (4-5).

In each of the above General Formulae, when a naphthyl group, acarbazolyl group, a fluorenyl group, a spirofluorenyl group, a phenylenegroup, or a biphenyldiyl group has a substituent, the substituent is analkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 25carbon atoms. Specific examples of the substituent include substituentsrepresented by Structural Formulae (5-1) to (5-31). Specific examples ofR¹¹ to R¹⁷, R²¹ to R²⁴, R⁴¹ to R⁴⁷, and R⁵¹ to R⁵⁴ include substituentsrepresented by Structural Formulae (5-1) to (5-31). Specific examples ofR³¹ to R³⁵ include substituents represented by Structural Formulae (5-1)to (5-8).

Specific examples of the organic compound represented by General Formula(G0) include organic compounds represented by Structural Formulae (100)to (157). Note that the present invention is not limited to thesecompounds.

A variety of reactions can be applied to a synthesis method of any ofthe organic compounds of embodiments of the present invention. Forexample, Step 1 and Step 2 described below enable the synthesis of theorganic compound of one embodiment of the present invention representedby General Formula (G0). Note that the synthesis method of any of theorganic compounds of embodiments of the present invention is not limitedto the synthesis methods below.

<Step 1>

As shown in Synthesis Scheme (A-1), coupling of primary arylamine (a1)and halogenated aryl (a2) is performed in the presence of a base using ametal catalyst, so that secondary diarylamine (a3) can be obtained.

In Synthesis Scheme (A-1), Ar¹ represents a naphthyl group; Ar²represents a carbazolyl group; α¹ and α² each independently represent aphenylene group or a biphenyldiyl group; and X¹ represents a halogengroup or a trifluoromethanesulfonyl group, preferably represents a bromogroup or an iodine group. The naphthyl group, the carbazolyl group, thephenylene group, and the biphenyldiyl group are each independentlyunsubstituted or substituted. In the case where any of the groups has asubstituent, the substituent is an alkyl group having 1 to 10 carbonatoms or an aryl group having 6 to 25 carbon atoms.

[Case of Performing Buchwald-Hartwig Reaction]

As a palladium catalyst that can be used in Synthesis Scheme (A-1),bis(dibenzylideneacetone)palladium(0) and palladium(II) acetate aregiven, for example. As a ligand of the palladium catalyst,tris(tert-butyl)phosphine, tri(n-hexyl)phosphine, andtricyclohexylphosphine are given, for example. The catalyst and theligand which can be used are not limited thereto.

Examples of bases that can be used in Synthesis Scheme (A-1) include anorganic base such as sodium tert-butoxide and an inorganic base such aspotassium carbonate. Examples of solvents that can be used in SynthesisScheme (A-1) include toluene, xylene, benzene, and tetrahydrofuran. Notethat the base and the solvent which can be used are not limited thereto.

[Case of Performing Ullmann Reaction]

In Synthesis Scheme (A-1), R¹⁰¹ and R¹⁰² each independently representhalogen, an acetyl group, or the like, and as halogen, chlorine,bromine, or iodine can be used. Furthermore, it is preferable to usecopper(I) iodide in which R¹⁰¹ is iodine or copper(II) acetate in whichR¹⁰² is an acetyl group. The copper compound used for the reaction isnot limited thereto. Further, copper can be used other than the coppercompound. A base that can be used in Synthesis Scheme (A-1) may be, butnot limited to, potassium carbonate. The base that can be used is notlimited thereto.

Examples of solvents that can be used in Synthesis Scheme (A-1) include1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)pyrimidinone (DMPU), toluene,xylene, and benzene. The solvent that can be used is not limitedthereto. In the Ullmann reaction, when the reaction temperature is 100°C. or higher, an objective substance can be obtained in a shorter timein a higher yield; therefore, it is preferable to use DMPU, xylene, ortoluene each having a high boiling point. The reaction temperature of150° C. or higher is further preferable; thus, DMPU is more preferablyused.

<Step 2>

As shown in Synthesis Scheme (A-2), coupling of secondary diarylamine(a3) and halogenated aryl (a4) is performed in the presence of a baseusing a metal catalyst, so that the organic compound represented byGeneral Formula (G0) can be obtained.

In Synthesis Scheme (A-2), Ar¹ represents a naphthyl group; Ar²represents a carbazolyl group; Ar³ represents a fluorenyl group or aspirofluorenyl group; α¹ and α² each independently represent a phenylenegroup or a biphenyldiyl group; and X² represents a halogen group or atrifluoromethanesulfonyl group, preferably represents a bromo group oran iodine group. The naphthyl group, the carbazolyl group, the fluorenylgroup, the spirofluorenyl group, the phenylene group, and thebiphenyldiyl group are each independently unsubstituted or substituted.In the case where any of the groups has a substituent, the substituentis an alkyl group having 1 to 10 carbon atoms or an aryl group having 6to 25 carbon atoms.

[Case of Performing Buchwald-Hartwig Reaction]

In the case of performing the Buchwald-Hartwig reaction, a palladiumcatalyst, a ligand of the palladium catalyst, a base, and a solventwhich can be used in Synthesis Scheme (A-2) can be similar to those inSynthesis Scheme (A-1).

[Case of Performing Ullmann Reaction]

In Synthesis Scheme (A-2), R¹⁰³ and R¹⁰⁴ each independently representhalogen, an acetyl group, or the like, and as halogen, chlorine,bromine, or iodine can be used. Furthermore, it is preferable to usecopper(I) iodide in which R¹⁰³ is iodine or copper(II) acetate in whichR¹⁰⁴ is an acetyl group. The copper compound used for the reaction isnot limited thereto. Further, copper can be used other than the coppercompound.

A base and a solvent which can be used in Synthesis Scheme (A-2) can besimilar to those in Synthesis Scheme (A-1).

Through the above-described steps, the organic compound of thisembodiment can be synthesized.

The organic compound of this embodiment has a high hole-transportproperty and thus can be suitably used as a material for ahole-transport layer of a light-emitting element. Furthermore, in thelight-emitting element, the organic compound can be suitably used as ahost material that disperses light-emitting substances in alight-emitting layer. The light-emitting layer may contain alight-emitting substance and a host material having a highelectron-transport property, and may further contain the organiccompound of this embodiment as an assist material. With the use of theorganic compound of this embodiment, a long-lifetime light-emittingelement can be achieved. Furthermore, with the use of the light-emittingelement, a light-emitting device, an electronic device, and a lightingdevice each having high reliability can be obtained.

This embodiment can be freely combined with any of the otherembodiments.

Embodiment 2

In this embodiment, a light-emitting element of one embodiment of thepresent invention will be described with reference to FIGS. 1A and 1B.

The light-emitting element described in this embodiment includes a pairof electrodes (a first electrode and a second electrode) and a layercontaining a light-emitting organic compound (EL layer) provided betweenthe pair of electrodes. One of the pair of electrodes serves as an anodeand the other serves as a cathode.

Specific examples of a structure of the light-emitting element of oneembodiment of the present invention are described below.

A light-emitting element illustrated in FIG. 1A includes an EL layer 203between a first electrode 201 and a second electrode 205. In thisembodiment, the first electrode 201 serves as an anode and the secondelectrode 205 serves as a cathode.

When a voltage higher than the threshold voltage of the light-emittingelement is applied between the first electrode 201 and the secondelectrode 205, holes are injected from the first electrode 201 side tothe EL layer 203 and electrons are injected from the second electrode205 side to the EL layer 203. The injected electrons and holes arerecombined in the EL layer 203 and a light-emitting substance containedin the EL layer 203 emits light.

The EL layer 203 includes at least a light-emitting layer containing alight-emitting substance. In addition to the light-emitting layer, theEL layer 203 may further include one or more layers containing any of asubstance with a high hole-injection property, a substance with a highhole-transport property, a hole-blocking material, a substance with ahigh electron-transport property, a substance with a highelectron-injection property, a substance with a bipolar property (asubstance with a high electron-transport property and a highhole-transport property), and the like.

A known substance can be used for the EL layer 203. Either a lowmolecular compound or a high molecular compound can be used, and aninorganic compound may be contained in the EL layer 203. In thisembodiment, the EL layer 203 contains the organic compound of oneembodiment of the present invention. The organic compound of oneembodiment of the present invention has a high hole-transport property,and thus can be used for a hole-transport layer or a light-emittinglayer.

A specific example of a structure of the EL layer 203 is illustrated inFIG. 1B. In the EL layer 203 illustrated in FIG. 1B, a hole-injectionlayer 301, a hole-transport layer 302, a light-emitting layer 303, anelectron-transport layer 304, and an electron-injection layer 305 arestacked in this order from the first electrode 201 side.

A light-emitting element illustrated in FIG. 1C includes the EL layer203 between the first electrode 201 and the second electrode 205, andfurther includes an intermediate layer 207 between the EL layer 203 andthe second electrode 205.

A specific example of a structure of the intermediate layer 207 isillustrated in FIG. 1D. The intermediate layer 207 includes at least acharge-generation region 308. In addition to the charge-generationregion 308, the intermediate layer 207 may further include anelectron-relay layer 307 and an electron-injection buffer layer 306. InFIG. 1D, the EL layer 203 is provided over the first electrode 201, theintermediate layer 207 is provided over the EL layer 203, and the secondelectrode 205 is provided over the intermediate layer 207. Also in FIG.1D, as the intermediate layer 207, the electron-injection buffer layer306, the electron-relay layer 307, and the charge-generation region 308are provided in this order from the EL layer 203 side.

When a voltage higher than the threshold voltage of the light-emittingelement is applied between the first electrode 201 and the secondelectrode 205, holes and electrons are generated in thecharge-generation region 308, and the holes move into the secondelectrode 205 and the electrons move into the electron-relay layer 307.The electron-relay layer 307 has a high electron-transport property andimmediately transfers the electrons generated in the charge-generationregion 308 to the electron-injection buffer layer 306. Theelectron-injection buffer layer 306 reduces a barrier against electroninjection into the EL layer 203, so that the efficiency of the electroninjection into the EL layer 203 can be improved. Thus, the electronsgenerated in the charge-generation region 308 are injected into thelowest unoccupied molecular orbital (LUMO) level of the EL layer 203through the electron-relay layer 307 and the electron-injection bufferlayer 306.

In addition, the electron-relay layer 307 can prevent reaction at theinterface between a material contained in the charge-generation region308 and a material contained in the electron-injection buffer layer 306.Thus, it is possible to prevent interaction such as damaging thefunctions of the charge-generation region 308 and the electron-injectionbuffer layer 306.

As illustrated in light-emitting elements in FIGS. 1E and 1F, aplurality of EL layers may be stacked between the first electrode 201and the second electrode 205. In that case, the intermediate layer 207is preferably provided between the stacked EL layers. For example, thelight-emitting element illustrated in FIG. 1E includes the intermediatelayer 207 between a first EL layer 203 a and a second EL layer 203 b.The light-emitting element illustrated in FIG. 1F includes n EL layers(n is a natural number of 2 or more). The light-emitting elementillustrated in FIG. 1F includes the intermediate layer 207 between anm-th EL layer 203(m) and an (m+1)-th EL layer 203(m+1).

The following will show behaviors of electrons and holes in theintermediate layer 207 between the EL layer 203(m) and the EL layer203(m+1). When a voltage higher than the threshold voltage of thelight-emitting element is applied between the first electrode 201 andthe second electrode 205, holes and electrons are generated in theintermediate layer 207, and the holes move into the EL layer 203(m+1)provided on the second electrode 205 side and the electrons move intothe EL layer 203(m) provided on the first electrode 201 side. The holesinjected into the EL layer 203(m+1) are recombined with the electronsinjected from the second electrode 205 side, so that a light-emittingsubstance contained in the EL layer 203(m+1) emits light. Further, theelectrons injected into the EL layer 203(m) are recombined with theholes injected from the first electrode 201 side, so that alight-emitting substance contained in the EL layer 203(m) emits light.Thus, the holes and electrons generated in the intermediate layer 207cause light emission in the respective EL layers.

Note that the EL layers can be provided in contact with each other aslong as the same structure as the intermediate layer is formedtherebetween. For example, when the charge-generation region is formedover one surface of an EL layer, another EL layer can be provided incontact with the surface.

Further, by forming EL layers to emit light of different colors fromeach other, a light-emitting element as a whole can provide lightemission of a desired color. For example, by forming a light-emittingelement having two EL layers such that the emission color of the firstEL layer and the emission color of the second EL layer are complementarycolors, the light-emitting element can provide white light emission as awhole. Note that the word “complementary” means color relationship inwhich an achromatic color is obtained when colors are mixed. That is,white light emission can be obtained by mixture of light from materialswhose emission colors are complementary colors. This can be applied to alight-emitting element having three or more EL layers.

FIGS. 1A to 1F can be used in an appropriate combination. For example,the intermediate layer 207 can be provided between the second electrode205 and the EL layer 203(n) in FIG. 1F.

Examples of materials which can be used for each layer will be describedbelow. Note that each layer is not limited to a single layer, and may bea stack of two or more layers.

<Anode>

The electrode serving as the anode (the first electrode 201 in thisembodiment) can be formed using one or more kinds of conductive metals,alloys, conductive compounds, and the like. In particular, it ispreferable to use a material with a high work function (4.0 eV or more).Examples include indium tin oxide (ITO), indium tin oxide containingsilicon or silicon oxide, indium zinc oxide, indium oxide containingtungsten oxide and zinc oxide, graphene, gold, platinum, nickel,tungsten, chromium, molybdenum, iron, cobalt, copper, palladium, and anitride of a metal material (e.g., titanium nitride).

When the anode is in contact with the charge-generation region, any of avariety of conductive materials can be used regardless of their workfunctions; for example, aluminum, silver, or an alloy containingaluminum can be used.

<Cathode>

The electrode serving as the cathode (the second electrode 205 in thisembodiment) can be formed using one or more kinds of conductive metals,alloys, conductive compounds, and the like. In particular, it ispreferable to use a material with a low work function (3.8 eV or less).Examples include aluminum, silver, an element belonging to Group 1 or 2of the periodic table (e.g., an alkali metal such as lithium or cesium,an alkaline earth metal such as calcium or strontium, or magnesium), analloy containing any of these elements (e.g., Mg—Ag or Al—Li), a rareearth metal such as europium or ytterbium, and an alloy containing anyof these rare earth metals.

When the cathode is in contact with the charge-generation region, any ofa variety of conductive materials can be used regardless of their workfunctions; for example, ITO or indium tin oxide containing silicon orsilicon oxide can be used.

The light-emitting element may have a structure in which one of theanode and the cathode is formed using a conductive film that transmitsvisible light and the other is formed using a conductive film thatreflects visible light, or a structure in which both the anode and thecathode are formed using conductive films that transmit visible light.

The conductive film that transmits visible light can be formed using,for example, indium oxide, ITO, indium zinc oxide, zinc oxide, or zincoxide to which gallium is added. Alternatively, a film of a metalmaterial such as gold, platinum, nickel, tungsten, chromium, molybdenum,iron, cobalt, copper, palladium, or titanium, or a nitride of any ofthese metal materials (e.g., titanium nitride) can be formed thin so asto have a light-transmitting property. Further alternatively, grapheneor the like may be used.

The conductive film that reflects visible light can be formed using, forexample, a metal material such as aluminum, gold, platinum, silver,nickel, tungsten, chromium, molybdenum, iron, cobalt, copper, orpalladium; an aluminum-containing alloy (aluminum alloy) such as analloy of aluminum and titanium, an alloy of aluminum and nickel, or analloy of aluminum and neodymium; or a silver-containing alloy such as analloy of silver and copper. An alloy of silver and copper is preferablebecause of its high heat resistance. Further, lanthanum, neodymium, orgermanium may be added to the metal material or the alloy.

The electrodes may be formed separately by a vacuum evaporation methodor a sputtering method. Alternatively, when a silver paste or the likeis used, a coating method or an inkjet method may be used.

<Hole-Injection Layer 301>

The hole-injection layer 301 contains a substance with a highhole-injection property.

Examples of the substance with a high hole-injection property includemetal oxides such as molybdenum oxide, titanium oxide, vanadium oxide,rhenium oxide, ruthenium oxide, chromium oxide, zirconium oxide, hafniumoxide, tantalum oxide, silver oxide, tungsten oxide, and manganeseoxide.

Alternatively, it is possible to use a phthalocyanine-based compoundsuch as phthalocyanine (abbreviation: H₂Pc) or copper(II) phthalocyanine(abbreviation: CuPc).

Further alternatively, it is possible to use an aromatic amine compoundwhich is a low molecular organic compound, such as4,4′,4″-tris(N,N-diphenylamino)triphenylamine (abbreviation: TDATA),4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine(abbreviation: MTDATA),4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation:DPAB),4,4′-bis(N-{4-[N′-(3-methylphenyl)-N′-phenylamino]phenyl}-N-phenylamino)biphenyl(abbreviation: DNTPD),1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene(abbreviation: DPA3B),3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA1),3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA2), or3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole(abbreviation: PCzPCN1).

Further alternatively, it is possible to use a high molecular compoundsuch as poly(N-vinylcarbazole) (abbreviation: PVK),poly(4-vinyltriphenylamine) (abbreviation: PVTPA),poly[N-(4-{N′-[4-(4-diphenylamino)phenyl]phenyl-N′-phenylamino}phenyl)methacrylamide](abbreviation: PTPDMA), orpoly[N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine] (abbreviation:Poly-TPD), or a high molecular compound to which acid is added, such aspoly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid) (PEDOT/PSS)or polyaniline/poly(styrenesulfonic acid) (PAni/PSS).

The hole-injection layer 301 may serve as the charge-generation region.When the hole-injection layer 301 in contact with the anode serves asthe charge-generation region, a variety of conductive materials can beused for the anode regardless of their work functions. Materialscontained in the charge-generation region will be described later.

<Hole-Transport Layer 302>

The hole-transport layer 302 contains a substance with a highhole-transport property. The organic compound of one embodiment of thepresent invention has a high hole-transport property, and thus can besuitably used for the hole-transport layer 302.

The substance with a high hole-transport property is preferably asubstance with a property of transporting more holes than electrons, andis especially preferably a substance with a hole mobility of 10⁻⁶cm²/V·s or more.

For the hole-transport layer 302, it is possible to use an aromaticamine compound such as 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl(abbreviation: NPB or α-NPD),N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine(abbreviation: TPD), 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine(abbreviation: BPAFLP),4,4′-bis[N-(9,9-dimethylfluoren-2-yl)-N-phenylamino]biphenyl(abbreviation: DFLDPB i), or4,4′-bis[N-(spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl(abbreviation: BSPB).

Alternatively, it is possible to use a carbazole derivative such as4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP),9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA),or 9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole(abbreviation: PCzPA).

Further alternatively, it is possible to use an aromatic hydrocarboncompound such as 2-tert-butyl-9,10-di(2-naphthyl)anthracene(abbreviation: t-BuDNA), 9,10-di(2-naphthyl)anthracene (abbreviation:DNA), or 9,10-diphenylanthracene (abbreviation: DPAnth).

Further alternatively, it is possible to use a high molecular compoundsuch as PVK, PVTPA, PTPDMA, or Poly-TPD.

<Light-Emitting Layer 303>

The light-emitting layer 303 contains a light-emitting substance. As thelight-emitting substance, a fluorescent compound which emitsfluorescence or a phosphorescent compound which emits phosphorescencecan be used.

Examples of fluorescent compounds that can be used for thelight-emitting layer 303 are given. Examples of materials that emit bluelight are as follows:N,N′-bis[4-(9H-carbazol-9-yl)phenyl]-N,N′-diphenylstilbene-4,4′-diamine(abbreviation: YGA2S),4-(9H-carbazol-9-yl)-4′-(10-phenyl-9-anthryl)triphenylamine(abbreviation: YGAPA), and4-(10-phenyl-9-anthryl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBAPA). Examples of materials that emit green light areas follows: N-(9,10-diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazol-3-amine(abbreviation: 2PCAPA),N-[9,10-bis(1,1′-biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazol-3-amine(abbreviation: 2PCABPhA),N-(9,10-diphenyl-2-anthryl)-N,N′,N′-triphenyl-1,4-phenylenediamineabbreviation: 2DPAPA),N-[9,10-bis(1,1′-biphenyl-2-yl)-2-anthryl]-N,N′,N′-triphenyl-1,4-phenylenediamine(abbreviation: 2DPABPhA),N-[9,10-bis(1,1′-biphenyl-2-yl)]-N-[4-(9H-carbazol-9-yl)phenyl]-N-phenylanthracen-2-amine(abbreviation: 2YGABPhA), and N,N,9-triphenylanthracen-9-amine(abbreviation: DPhAPhA). Examples of materials that emit yellow lightare as follows: rubrene and5,12-bis(1,1′-biphenyl-4-yl)-6,11-diphenyltetracene (abbreviation: BPT).Examples of materials that emit red light are as follows:N,N,N′,N′-tetrakis(4-methylphenyl)tetracene-5,11-diamine (abbreviation:p-mPhTD) and7,14-diphenyl-N,N,N′,N′-tetrakis(4-methylphenyl)acenaphtho[1,2-α]fluoranthene-3,10-diamine(abbreviation: p-mPhAFD).

Examples of phosphorescent compounds that can be used for thelight-emitting layer 303 are given. For example, a phosphorescentcompound having an emission peak at 440 nm to 520 nm is given, examplesof which include organometallic iridium complexes having 4H-triazoleskeletons, such astris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-kN²]phenyl-kC}iridium(III) (abbreviation: [Ir(mpptz-dmp)₃]),tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III)(abbreviation: [Ir(Mptz)₃]), andtris[4-(3-biphenylyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazolato]iridium(III) (abbreviation: [Ir(iPrptz-3b)₃]); organometallic iridium complexeshaving 1H-triazole skeletons, such astris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III) (abbreviation: [Ir(Mptz1-mp)₃]) andtris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III)(abbreviation: [Ir(Prptz1-Me)₃]); organometallic iridium complexeshaving imidazole skeletons, such asfac-tris[1-(2,6-diisopropylphenyl)-2-phenyl-1H-imidazole]iridium(III)(abbreviation: [Ir(iPrpmi)₃]) andtris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III)(abbreviation: [Ir(dmpimpt-Me)₃]); and organometallic iridium complexesin which aphenylpyridine derivative having an electron-withdrawing groupis a ligand, such as bis[2-(4′,6′-difluorophenyl)pyridinato-N,C²]iridium(III) tetrakis(1-pyrazolyl)borate (abbreviation: FIr6),bis[2-(4′,6′-difluorophenyl)pyridinato-N,C²]iridium(III) picolinate(abbreviation: FIrpic),bis{2-[3′,5′-bis(trifluoromethyl)phenyl]pyridinato-N,C²′}iridium(III)picolinate (abbreviation: [Ir(CF₃ppy)₂(pic)]), andbis[2-(4′,6′-difluorophenyl)pyridinato-N,C²′]iridium(III)acetylacetonate (abbreviation: Firacac). Among the materials givenabove, the organometallic iridium complex having a 4H-triazole skeletonhas high reliability and high emission efficiency and is thus especiallypreferable.

Examples of the phosphorescent compound having an emission peak at 520nm to 600 nm include organometallic iridium complexes having pyrimidineskeletons, such as tris(4-methyl-6-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(mppm)₃]),tris(4-t-butyl-6-phenylpyrimidinato)iridium(III) (abbreviation:[Ir(tBuppm)₃]),(acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium (III)(abbreviation: [Ir(mppm)₂(acac)]),(acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(tBuppm)₂(acac)]),(acetylacetonato)bis[4-(2-norbornyl)-6-phenylpyrimidinato]iridium(III)(abbreviation: [Ir(nbppm)₂(acac)]),(acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iridium(III)(abbreviation: [Ir(mpmppm)₂(acac)]), and(acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III)(abbreviation: [Ir(dppm)₂(acac)]); organometallic iridium complexeshaving pyrazine skeletons, such as(acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium (III)(abbreviation: [Ir(mppr-Me)₂(acac)]) and(acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III) (abbreviation: [Ir(mppr-iPr)₂(acac)]); organometallic iridiumcomplexes having pyridine skeletons, such astris(2-phenylpyridinato-N,C²′)iridium(III) (abbreviation: [Ir(ppy)₃]),bis(2-phenylpyridinato-N,C²′) iridium(III) acetylacetonate(abbreviation: [Ir(ppy)₂(acac)]), bis(benzo[h]quinolinato)iridium(III)acetylacetonate (abbreviation: [Ir(bzq)₂(acac)]),tris(benzo[h]quinolinato)iridium (III) (abbreviation: [Ir(bzq)₃]),tris(2-phenylquinolinato-N,C²′)iridium(III) (abbreviation: [Ir(pq)₃]),and bis(2-phenylquinolinato-N,C²′)iridium(III) acetylacetonate(abbreviation: [Ir(pq)₂(acac)]); and a rare earth metal complex such astris(acetylacetonato) (monophenanthroline)terbium(III) (abbreviation:[Tb(acac)₃(Phen)]).

Examples of the phosphorescent material having an emission peak at 600nm to 700 nm include organometallic iridium complexes having pyrimidineskeletons, such as(diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III)(abbreviation: [Ir(5mdppm)₂(dibm)]),bis[4,6-bis(3-methylphenyl)pyrimidinato](dipivaloylmethanate)iridium(III)(abbreviation: [Ir(5mdppm)₂(dpm)]), andbis[4,6-di(naphthalen-1-yl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: [Ir(dlnpm)₂(dpm)]); organometallic iridiumcomplexes having pyrazine skeletons, such as(acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III)(abbreviation: [Ir(tppr)₂(acac)]),bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III)(abbreviation: [Ir(tppr)₂(dpm)]), or(acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III)(abbreviation: [Ir(Fdpq)₂(acac)]); organometallic iridium complexeshaving pyridine skeletons, such astris(1-phenylisoquinolinato-N,C²′)iridium(III) (abbreviation:[Ir(piq)₃]) andbis(1-phenylisoquinolinato-N,C²′)iridium(III)acetylacetonate(abbreviation: [Ir(piq)₂(acac)]); a platinum complex such as2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II)(abbreviation: PtOEP); and rare earth metal complexes such astris(1,3-diphenyl-1,3-propanedionato) (monophenanthroline)europium (III)(abbreviation: [Eu(DBM)₃(Phen)]) andtris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III) (abbreviation: [Eu(TTA)₃(Phen)]).Among the materials given above, the organometallic iridium complexhaving a pyrimidine skeleton has distinctively high reliability andemission efficiency and is thus especially preferable. Furthermore, theorganometallic iridium complex having a pyrazine skeleton can providered light emission with favorable chromaticity.

Alternatively, a high molecular compound can be used for thelight-emitting layer 303. Examples of the materials that emit blue lightinclude poly(9,9-dioctylfluorene-2,7-diyl) (abbreviation: PFO),poly[(9,9-dioctylfluorene-2,7-diyl-co-(2,5-dimethoxybenzene-1,4-diyl)](abbreviation: PF-DMOP), andpoly{(9,9-dioctylfluorene-2,7-diyl)-co-[N,N′-di-(p-butylphenyl)-1,4-diaminobenzene]}(abbreviation: TAB-PFH). Examples of the materials that emit green lightinclude poly(p-phenylenevinylene) (abbreviation: PPV),poly[(9,9-dihexylfluorene-2,7-diyl)-alt-co-(benzo[2,1,3]thiadiazole-4,7-diyl)] (abbreviation: PFBT), andpoly[(9,9-dioctylfluorene-2,7-divinylenefluorenylene)-alt-co-(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene)]. Examples of the materials that emit orange tored light includepoly[2-methoxy-5-(2′-ethylhexoxy)-1,4-phenylenevinylene] (abbreviation:MEH-PPV), poly(3-butylthiophene-2,5-diyl) (abbreviation: R⁴-PAT),poly{[9,9-dihexyl-2,7-bis(1-cyanovinylene)fluorenylene]-alt-co-[2,5-bis(N,N′-diphenylamino)-1,4-phenylene]}, and poly{[2-methoxy-5-(2-ethylhexyloxy)-1,4-bis(1-cyanovinylenephenylene)]-alt-co-[2,5-bis(N,N′-diphenylamino)-1,4-phenylene]}(abbreviation: CN-PPV-DPD).

Note that the light-emitting layer 303 may have a structure in which anyof the above light-emitting substances (a guest material) is dispersedin another substance (a host material). As the host material, a varietyof kinds of materials can be used, and it is preferable to use asubstance which has a lowest unoccupied molecular orbital level (LUMOlevel) higher than that of the guest material and has a highest occupiedmolecular orbital level (HOMO level) lower than that of the guestmaterial. With the structure in which the guest material is dispersed inthe host material, crystallization of the light-emitting layer 303 canbe suppressed. Furthermore, concentration quenching due to highconcentration of the guest material can be suppressed.

As the host material, the above-described substance having a highhole-transport property (e.g., an aromatic amine compound or a carbazolederivative) or a later-described substance having a highelectron-transport property (e.g., a metal complex having a quinolineskeleton or a benzoquinoline skeleton or a metal complex having anoxazole-based or thiazole-based ligand) can be used, for example. Theorganic compound of one embodiment of the present invention has a highhole-transport property and can be suitably used as the material.Specific examples of the host material are as follows: metal complexes,such as tris(8-quinolinolato)aluminum(III) (abbreviation: Alq),tris(4-methyl-8-quinolinolato)aluminum(III) (abbreviation: Almq₃),bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq₂),bis[2-(2′-hydroxyphenyl)pyridinato]zinic(II) (abbreviation: Znpp₂),bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III)(abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq),bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: Zn(BOX)₂),bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: Zn(BTZ)₂);heterocyclic compounds, such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7),3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole(abbreviation: TAZ),2,2′,2″-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole)(abbreviation: TPBI), bathophenanthroline (abbreviation: BPhen), andbathocuproine (abbreviation: BCP); carbazole derivatives, such as CzPAand 3,6-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole(abbreviation: DPCzPA); aromatic hydrocarbon compounds or condensedaromatic compounds, such as DNA, t-BuDNA, DPAnth,9,10-bis(3,5-diphenylphenyl)anthracene (abbreviation: DPPA), 9,9′-bianthryl (abbreviation: BANT),9,9′-(stilbene-3,3′-diyl)diphenanthrene (abbreviation: DPNS),9,9′-(stilbene-4,4′-diyl)diphenanthrene (abbreviation: DPNS2),3,3′,3″-(benzene-1,3,5-triyl)tripyrene (abbreviation: TPB3), and6,12-dimethoxy-5,11-diphenylchrysene; aromatic amine compounds, such asN,N-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: CzAlPA), 4-(10-phenyl-9-anthryl)triphenylamine(abbreviation: DPhPA),N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: PCAPA),N,9-diphenyl-N-{4-[4-(10-phenyl-9-anthryl)phenyl]phenyl}-9H-carbazol-3-amine(abbreviation: PCAPBA), N-(9,10-diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazol-3-amine (abbreviation:2PCAPA), NPB, TPD, DFLDPBi, and BSPB.

Alternatively, the followings can be used: compounds having an arylamineskeleton, such as 4-phenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBAlBP), PCzPCN1, and2,3-bis(4-diphenylaminophenyl)quinoxaline (abbreviation: TPAQn);carbazole derivatives, such as CBP and4,4′,4″-tris(N-carbazolyl)triphenylamine (abbreviation: TCTA); andnitrogen-containing heteroaromatic compounds, such as2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[g,h]quinoxaline (abbreviation:2mDBTPDBq-II),2-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline(abbreviation: 2mDBTBPDBq-II), and2-[4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl]dibenzo quinoxaline(abbreviation: 2CzPDBq-III). Further alternatively, a high molecularcompound such as PVK can be used.

As the host material, plural kinds of materials can be used. Forexample, in order to suppress crystallization, a substance such asrubrene which suppresses crystallization, may be further added. Inaddition, NPB, Alq, or the like may be further added in order toefficiently transfer energy to the guest material.

Further, when a plurality of light-emitting layers are provided andemission colors of the layers are made different, light emission of adesired color can be obtained from the light-emitting element as awhole. For example, the emission colors of first and secondlight-emitting layers are complementary in a light-emitting elementhaving the two light-emitting layers, so that the light-emitting elementcan be made to emit white light as a whole. Further, the same applies toa light-emitting element having three or more light-emitting layers.

<Electron-Transport Layer 304>

The electron-transport layer 304 contains a substance with a highelectron-transport property.

The substance with a high electron-transport property is preferably anorganic compound having a property of transporting more electrons thanholes, and is especially preferably a substance with an electronmobility of 10⁻⁶ cm²/V·s or more.

For example, metal complexes such as Alq, Almq₃, BeBq₂, BAlq, Zn(BOX)₂,and Zn(BTZ)₂ can be used.

Alternatively, heteroaromatic compounds such as PBD, OXD-7, TAZ, BPhen,BCP,3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: p-EtTAZ), 4,4′-bis(5-methylbenzoxazol-2-yl)stilbene(abbreviation: BzOs) can be used.

Further alternatively, it is possible to use a high molecular compoundsuch as poly(2,5-pyridinediyl) (abbreviation: PPy),poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)](abbreviation:PF-Py) orpoly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2′-bipyridine-6,6′-diyl)](abbreviation: PF-BPy).

<Electron-Injection Layer 305>

The electron-injection layer 305 contains a substance with a highelectron-injection property.

Examples of the substance with a high electron-injection propertyinclude an alkali metal, an alkaline earth metal, a rare earth metal,and a compound thereof (e.g., an oxide thereof, a carbonate thereof, anda halide thereof), such as lithium, cesium, calcium, lithium oxide,lithium carbonate, cesium carbonate, lithium fluoride, cesium fluoride,calcium fluoride, and erbium fluoride.

The electron-injection layer 305 may contain the above-describedsubstance with a high electron-transport property and a donor substance.For example, the electron-injection layer 305 may be formed using an Alqlayer containing magnesium (Mg). When the substance with a highelectron-transport property and the donor substance are contained, themass ratio of the donor substance to the substance with a highelectron-transport property is from 0.001:1 to 0.1:1.

Examples of the donor substance include an alkali metal, an alkalineearth metal, a rare earth metal, and a compound thereof (an oxidethereof), such as lithium, cesium, magnesium, calcium, erbium,ytterbium, lithium oxide, calcium oxide, barium oxide, and magnesiumoxide; a Lewis base; and an organic compound such as tetrathiafulvalene(abbreviation: TTF), tetrathianaphthacene (abbreviation: TTN),nickelocene, or decamethylnickelocene.

<Charge-Generation Region>

The charge-generation region included in the hole-injection layer andthe charge-generation region 308 each contain a substance with a highhole-transport property and an acceptor substance (electron acceptor).The acceptor substance is preferably added such that the mass ratio ofthe acceptor substance to the substance with a high hole-transportproperty is 0.1:1 to 4.0:1.

The charge-generation region is not limited to a structure in which asubstance with a high hole-transport property and an acceptor substanceare contained in the same film, and may have a structure in which alayer containing a substance with a high hole-transport property and alayer containing an acceptor substance are stacked. Note that in thecase of a stacked-layer structure in which the charge-generation regionis provided on the cathode side, the layer containing the substance witha high hole-transport property is in contact with the cathode, and inthe case of a stacked-layer structure in which the charge-generationregion is provided on the anode side, the layer containing the acceptorsubstance is in contact with the anode.

The substance with a high hole-transport property is preferably anorganic compound having a property of transporting more holes thanelectrons, and is especially preferably an organic compound with a holemobility of 10⁻⁶ cm²/V·s or more.

Specifically, it is possible to use any of the materials with a highhole-transport property shown as materials that can be used for thehole-transport layer 302, such as an organic compound of one embodimentof the present invention, aromatic amine compounds such as NPB andBPAFLP, carbazole derivatives such as CBP, CzPA, and PCzPA, aromatichydrocarbon compounds such as t-BuDNA, DNA, and DPAnth, and highmolecular compounds such as PVK and PVTPA.

Examples of the acceptor substance include organic compounds, such as7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation:F₄-TCNQ) and chloranil, oxides of transition metals, and oxides ofmetals that belong to Groups 4 to 8 in the periodic table. Specifically,vanadium oxide, niobium oxide, tantalum oxide, chromium oxide,molybdenum oxide, tungsten oxide, manganese oxide, and rhenium oxide arepreferable since their electron-accepting property is high. Inparticular, use of molybdenum oxide is preferable because of itsstability in the air, a low hygroscopic property, and easily handling.

<Electron-Injection Buffer Layer 306>

The electron-injection buffer layer 306 contains a substance with a highelectron-injection property. The electron-injection buffer layer 306facilitates electron injection from the charge-generation region 308into the EL layer 203. As the material having a high electron-injectionproperty, any of the above-described materials can be used.Alternatively, the electron-injection buffer layer 306 may contain anyof the above-described materials with a high electron-transport propertyand donor substances.

<Electron-Relay Layer 307>

The electron-relay layer 307 immediately accepts electrons drawn out ofthe acceptor substance in the charge-generation region 308.

The electron-relay layer 307 contains a substance with a highelectron-transport property. As the substance with a highelectron-transport property, a phthalocyanine-based material or a metalcomplex having a metal-oxygen bond and an aromatic ligand is preferablyused.

As the phthalocyanine-based material, specifically, it is possible touse CuPc, a phthalocyanine tin(II) complex (SnPc), a phthalocyanine zinccomplex (ZnPc), cobalt(II) phthalocyanine, β-form (CoPc), phthalocyanineiron (FePc), vanadyl 2,9,16,23-tetraphenoxy-29H,31H-phthalocyanine(PhO-VOPc), or the like.

As the metal complex having a metal-oxygen bond and an aromatic ligand,a metal complex having a metal-oxygen double bond is preferably used. Ametal-oxygen double bond has an acceptor property; thus, electrons cantransfer (be donated and accepted) more easily.

As the metal complex having a metal-oxygen bond and an aromatic ligand,a phthalocyanine-based material is also preferably used. In particular,vanadyl phthalocyanine (VOPc), a phthalocyanine tin(IV) oxide complex(SnOPc), or a phthalocyanine titanium oxide complex (TiOPc) ispreferable because a metal-oxygen double bond is more likely to act onanother molecule in terms of a molecular structure and an acceptorproperty is high.

As the phthalocyanine-based material, a phthalocyanine-based materialhaving a phenoxy group is preferably used. Specifically, aphthalocyanine derivative having a phenoxy group, such as PhO-VOPc, ispreferably used. The phthalocyanine derivative having a phenoxy group issoluble in a solvent; thus, the phthalocyanine derivative has anadvantage of being easily handled during formation of a light-emittingelement and an advantage of facilitating maintenance of an apparatusused for film formation.

Examples of other materials with a high electron-transport propertyinclude perylene derivatives such as 3,4,9,10-perylenetetracarboxylicdianhydride (abbreviation: PTCDA), 3,4,9,10-perylenetetracarboxylicbisbenzimidazole (abbreviation: PTCBI),N,N′-dioctyl-3,4,9,10-perylenetetracarboxylic diimide (abbreviation:PTCDI-C8H), N,N′-dihexyl-3,4,9,10-perylenetetracarboxylic diimide(abbreviation: Hex PTC), and the like. Alternatively, it is possible touse a nitrogen-containing condensed aromatic compound such aspirazino[2,3-f][1,10]phenanthroline-2,3-dicarbonitrile (abbreviation:PPDN), 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene(abbreviation: HAT(CN)₆), 2,3-diphenylpyrido[2,3-b]pyrazine(abbreviation: 2PYPR), or 2,3-bis(4-fluorophenyl)pyrido[2, 3-b]pyrazine(abbreviation: F2PYPR). The nitrogen-containing condensed aromaticcompound is preferably used for the electron-relay layer 307 because ofits stability.

Further alternatively, it is possible to use7,7,8,8-tetracyanoquinodimethane (abbreviation: TCNQ),1,4,5,8-naphthalenetetracarboxylicdianhydride (abbreviation: NTCDA),perfluoropentacene, copper hexadecafluoro phthalocyanine (abbreviation:F₁₆CuPc),N,N′-bis(2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctyl)-1,4,5,8-naphthalenetetracarboxylicdiimide (abbreviation: NTCDI-C8F),3′,4′-dibutyl-5,5″-bis(dicyanomethylene)-5,5″-dihydro-2,2′:5′,2″-terthiophene(abbreviation: DCMT), or a methanofullerene (e.g., [6,6]-phenyl C₆₁butyric acid methyl ester).

The electron-relay layer 307 may further contain any of theabove-described donor substances. When the donor substance is containedin the electron-relay layer 307, electrons can transfer easily and thelight-emitting element can be driven at a lower voltage.

The LUMO levels of the substance with a high electron-transport propertyand the donor substance are preferably −5.0 eV to −3.0 eV, i.e., betweenthe LUMO level of the acceptor substance contained in thecharge-generation region 308 and the LUMO level of the substance with ahigh electron-transport property contained in the electron-transportlayer 304 (or the LUMO level of the EL layer 203 in contact with theelectron-relay layer 307 through the electron-injection buffer layer306). When a donor substance is contained in the electron-relay layer307, as the substance with a high electron-transport property, asubstance with a LUMO level higher than the acceptor level of theacceptor substance contained in the charge-generation region 308 can beused.

The above-described layers included in the EL layer 203 and theintermediate layer 207 can be formed separately by any of the followingmethods: an evaporation method (including a vacuum evaporation method),a transfer method, a printing method, an inkjet method, a coatingmethod, and the like.

By use of a light-emitting element described in this embodiment, apassive matrix light-emitting device or an active matrix light-emittingdevice in which driving of the light-emitting element is controlled by atransistor can be manufactured. Furthermore, the light-emitting devicecan be applied to an electronic device, a lighting device, and the like.

This embodiment can be freely combined with any of the otherembodiments.

Embodiment 3

In this embodiment, a light-emitting element of one embodiment of thepresent invention will be described with reference to FIG. 2.

A light-emitting element illustrated in FIG. 2 includes the EL layer 203between the first electrode 201 and the second electrode 205. The ELlayer 203 includes at least a light-emitting layer 213 that contains afirst organic compound 221, a second organic compound 222, and aphosphorescent compound 223. In addition to the light-emitting layer213, the EL layer 203 may further include one or more layers containingany of a substance with a high hole-injection property, a substance witha high hole-transport property, a hole-blocking material, a substancewith a high electron-transport property, a substance with a highelectron-injection property, a substance with a bipolar property (asubstance with a high electron-transport property and a highhole-transport property), and the like.

The phosphorescent compound 223 is a guest material in thelight-emitting layer 213. In this embodiment, one of the first organiccompound 221 and the second organic compound 222, the content of whichin the light-emitting layer 213 is higher than that of the other, is ahost material in the light-emitting layer 213. The organic compound ofone embodiment of the present invention can be suitably used as thefirst organic compound 221 or the second organic compound 222.

When the light-emitting layer 213 has the structure in which the guestmaterial is dispersed in the host material, the crystallization of thelight-emitting layer can be suppressed. Further, it is possible tosuppress concentration quenching due to high concentration of the guestmaterial; thus, the light-emitting element can have higher emissionefficiency.

Note that it is preferable that a triplet excited energy level (T₁level) of each of the first organic compound 221 and the second organiccompound 222 be higher than that of the phosphorescent compound 223.This is because, when the T₁ level of the first organic compound 221 (orthe second organic compound 222) is lower than that of thephosphorescent compound 223, the triplet excited energy of thephosphorescent compound 223, which is to contribute to light emission,is quenched by the first organic compound 221 (or the second organiccompound 222) and accordingly, the emission efficiency decreases.

Here, for improvement in efficiency of energy transfer from a hostmaterial to a guest material, Førster mechanism (dipole-dipoleinteraction) and Dexter mechanism (electron exchange interaction), whichare known as mechanisms of energy transfer between molecules, areconsidered. According to the mechanisms, it is preferable that anemission spectrum of a host material (fluorescence spectrum in energytransfer from a singlet excited state, phosphorescence spectrum inenergy transfer from a triplet excited state) largely overlap with anabsorption spectrum of a guest material (specifically, spectrum in anabsorption band on the longest wavelength (lowest energy) side).

However, in general, it is difficult to obtain an overlap between afluorescence spectrum of a host material and an absorption spectrum inan absorption band on the longest wavelength (lowest energy) side of aguest material. The reason for this is as follows: if the fluorescencespectrum of the host material overlaps with the absorption spectrum inthe absorption band on the longest wavelength (lowest energy) side ofthe guest material, because the phosphorescence spectrum of the hostmaterial is located on the longer wavelength (lower energy) side thanthe fluorescence spectrum, the T₁ level of the host material becomeslower than the T₁ level of the phosphorescent compound and theabove-described problem of quenching occurs; yet, when the host materialis designed in such a manner that the T₁ level of the host material ishigher than the T₁ level of the phosphorescent compound to avoid theproblem of quenching, the fluorescence spectrum of the host material isshifted to the shorter wavelength (higher energy) side, and thus thefluorescence spectrum does not have any overlap with the absorptionspectrum in the absorption band on the longest wavelength (lowestenergy) side of the guest material. For this reason, in general, it isdifficult to obtain an overlap between a fluorescence spectrum of a hostmaterial and an absorption spectrum in an absorption band on the longestwavelength (lowest energy) side of a guest material so as to maximizeenergy transfer from a singlet excited state of a host material.

Thus, in one embodiment of the present invention, a combination of thefirst organic compound 221 and the second organic compound 222preferably forms an excited complex (also referred to as exciplex). Inthat case, the first organic compound 221 and the second organiccompound 222 form an exciplex at the time of recombination of carriers(electrons and holes) in the light-emitting layer 213. Thus, in thelight-emitting layer 213, a fluorescence spectrum of the first organiccompound 221 and that of the second organic compound 222 are convertedinto an emission spectrum of the exciplex which is located on a longerwavelength side. Moreover, when the first organic compound and thesecond organic compound are selected such that the emission spectrum ofthe exciplex largely overlaps with the absorption spectrum of the guestmaterial, energy transfer from a singlet excited state can be maximized.Note that also in the case of a triplet excited state, energy transferfrom the exciplex, not the host material, is considered to occur.

As the phosphorescent compound 223, for example, the phosphorescentcompound described in Embodiment 2 can be used. Although any combinationof the first organic compound 221 and the second organic compound 222can be used as long as an exciplex is formed, a compound which is likelyto accept electrons (a compound having an electron-trapping property)and a compound which is likely to accept holes (a compound having ahole-trapping property) are preferably combined.

As the compound which is likely to accept electrons, a π-electrondeficient heteroaromatic compound such as a nitrogen-containingheteroaromatic compound, a metal complex having a quinoline skeleton ora benzoquinoline skeleton, or a metal complex having an oxazole-basedligand or a thiazole-based ligand can be used, for example.

Specific examples are as follows: metal complexes such as BeBq₂, BAlq,Znq, Zn(BOX)₂, and Zn(BTZ)₂; heterocyclic compounds having a polyazoleskeleton, such as PBD, TAZ, OXD-7,9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation:CO11), 2,2′,2″-(1,3,5-Benzenetriyl)tris(1-phenyl-1H-benzimidazole)(abbreviation: TPBI), and2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole(abbreviation: mDBTBIm-II); heterocyclic compounds having a quinoxalineskeleton or a dibenzoquinoxaline skeleton, such as 2mDBTPDBq-II,2mDBTBPDBq-II, 2CzPDBq-III,7-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:7mDBTPDBq-II), 6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo quinoxaline(abbreviation: 6mDBTPDBq-II), and2-[3′-(9H-carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]inoxaline(abbreviation: 2mCzBPDBq); heterocyclic compounds having a diazineskeleton (a pyrimidine skeleton or a pyrazine skeleton), such as4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine (abbreviation:4,6mPnP2Pm), 4,6-bis[3-(9H-carbazol-9-yl)phenyl]pyrimidine(abbreviation: 4,6mCzP2Pm), and4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation:4,6mDBTP2Pm-II); and heterocyclic compounds having a pyridine skeleton,such as 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine,1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB), and3,3′,5,5′-tetra[(m-pyridyl)-phen-3-yl]biphenyl (abbreviation: BP4mPy).Among the above substances, the heterocyclic compounds having aquinoxaline skeleton or a dibenzoquinoxaline skeleton, the heterocycliccompounds having a diazine skeleton, and the heterocyclic compoundshaving a pyridine skeleton have high reliability and are thuspreferable.

As the compound which is likely to accept holes, the organic compound ofone embodiment of the present invention can be suitably used.Alternatively, a π-electron rich heteroaromatic compound (e.g., acarbazole derivative or an indole derivative) or an aromatic aminecompound can be suitably used, examples of which include PCBA1BP,4,4′-di(1-naphthyl)-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBNBB), PCzPCN1, 4,4′,4″-tris[N-(1-naphthyl)-N-phenylamino]triphenylamine (abbreviation: 1′-TNATA),2,7-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-spiro-9,9′-bifluorene(abbreviation: DPA2SF),N,N′-bis(9-phenylcarbazol-3-yl)-N,N′-diphenylbenzene-1,3-diamine(abbreviation: PCA2B),N-(9,9-dimethyl-2-diphenylamino-9H-fluoren-7-yl)diphenylamine(abbreviation: DPNF),N,N′,N″-triphenyl-N,N′,N″-tris(9-phenylcarbazol-3-yl)benzene-1,3,5-triamine(abbreviation: PCA3B),2-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]spiro-9,9′-bifluorene(abbreviation: PCASF), 2-[N-(4-diphenylaminophenyl)-N-phenylamino]spiro-9,9′-bifluorene (abbreviation: DPASF),N,N′-bis[4-(carbazol-9-yl)phenyl]-N,N′-diphenyl-9, 9-dimethylfluorene-2,7-diamine (abbreviation: YGA2F), TPD, DPAB,N-(9,9-dimethyl-9H-fluoren-2-yl)-N-{9,9-dimethyl-2-[N′-phenyl-N′-(9,9-dimethyl-9H-fluoren-2-yl)amino]-9H-fluoren-7-yl}phenylamine(abbreviation: DFLADFL), PCzPCA1,3-[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzDPA1),3,6-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzDPA2), DNTPD,3,6-bis[N-(4-diphenylaminophenyl)-N-(1-naphthyl)amino]-9-phenylcarbazole(abbreviation: PCzTPN2), and PCzPCA2.

The materials that can be used for the first organic compound 221 andthe second organic compound 222 are not limited to the above compoundsas long as the combination of the first organic compound 221 and thesecond organic compound 222 can form an exciplex, the emission spectrumof the exciplex overlaps with the absorption spectrum of thephosphorescent compound 223, and the peak of the emission spectrum ofthe exciplex has a longer wavelength than the peak of the absorptionspectrum of the phosphorescent compound 223.

Note that in the case where a compound which is likely to acceptelectrons and a compound which is likely to accept holes are used forthe first organic compound 221 and the second organic compound 222,carrier balance can be controlled by the mixture ratio of the compounds.Specifically, the ratio of the first organic compound to the secondorganic compound is preferably 1:9 to 9:1.

In the light-emitting element described in this embodiment, energytransfer efficiency can be improved owing to energy transfer utilizingan overlap between an emission spectrum of an exciplex and an absorptionspectrum of a phosphorescent compound; accordingly, the light-emittingelement can achieve high external quantum efficiency.

Note that in one embodiment of the present invention, the light-emittinglayer 213 can be formed using a host molecule having a hole-trappingproperty and a host molecule having an electron-trapping property as thetwo kinds of organic compounds other than the phosphorescent compound223 (guest material) so that a phenomenon (guest coupled withcomplementary hosts: GCCH) occurs in which holes and electrons areintroduced to guest molecules existing in the two kinds of hostmolecules and the guest molecules are brought into an excited state.

At this time, the host molecule having a hole-trapping property and thehost molecule having an electron-trapping property can be respectivelyselected from the above-described compounds which are likely to acceptholes and the above-described compounds which are likely to acceptelectrons.

This embodiment can be freely combined with any of the otherembodiments.

Embodiment 4

In this embodiment, a light-emitting device of one embodiment of thepresent invention will be described with reference to FIGS. 3A and 3B.FIG. 3A is a plan view of a light-emitting device of one embodiment ofthe present invention and FIG. 3B is a cross-sectional view taken alonga dashed-dotted line A-B in FIG. 3A.

In the light-emitting device of this embodiment, a light-emittingelement 403 (a first electrode 421, an EL layer 423, and a secondelectrode 425) is provided in a space 415 surrounded by a supportsubstrate 401, a sealing substrate 405, and a sealant 407. Thelight-emitting element 403 has a bottom emission structure.Specifically, the light-emitting element 403 includes the firstelectrode 421 that transmits visible light over the support substrate401, the EL layer 423 over the first electrode 421, and the secondelectrode 425 that reflects visible light over the EL layer 423.

One embodiment of the present invention is applied to the light-emittingelement 403. Specifically, a light-emitting layer included in the ELlayer 423 contains the organic compound of one embodiment of the presentinvention. Thus, the light-emitting element 403 has a long lifetime. Byapplication of one embodiment of the present invention, a highlyreliable light-emitting device can be achieved.

A first terminal 409 a is electrically connected to an auxiliary wiring417 and the first electrode 421. An insulating layer 419 is provided ina region which overlaps with the auxiliary wiring 417 over the firstelectrode 421. The first terminal 409 a and the second electrode 425 areelectrically insulated by the insulating layer 419. The second terminal409 b is electrically connected to the second electrode 425. Note thatalthough the first electrode 421 is formed over the auxiliary wiring 417in this embodiment, the auxiliary wiring 417 may be formed over thefirst electrode 421.

The organic EL element emits light in a region with a refractive indexhigher than that of the air; thus, when light is extracted to theatmosphere, total reflection occurs in the organic EL element or at theinterface between the organic EL element and the atmosphere under acertain condition, which results in a light extraction efficiency oflower than 100%.

Accordingly, for example, a light extraction structure 411 a ispreferably provided at an interface between the support substrate 401and the atmosphere. The refractive index of the support substrate 401 ishigher than that of the atmosphere. Therefore when provided at theinterface between the support substrate 401 and the atmosphere, thelight extraction structure 411 a can reduce light which cannot beextracted to the atmosphere due to total reflection, resulting in anincrease in the light extraction efficiency of the light-emittingdevice.

A light extraction structure 411 b is preferably provided at aninterface between the light-emitting element 403 and the supportsubstrate 401.

However, when the first electrode 421 has unevenness, leakage currentmight occur in the EL layer 423 formed over the first electrode 421.Therefore, in this embodiment, a planarization layer 413 having arefractive index higher than or equal to that of the EL layer 423 isprovided in contact with the light extraction structure 411 b. Thus, thefirst electrode 421 can be a flat film, and occurrence of leakagecurrent in the EL layer 423 due to the unevenness of the first electrode421 can be suppressed. Moreover, since the light extraction structure411 b is provided at an interface between the planarization layer 413and the support substrate 401, light which cannot be extracted to theatmosphere due to total reflection can be reduced, so that the lightextraction efficiency of the light-emitting device can be improved.

Note that in FIG. 3B, the support substrate 401, the light extractionstructure 411 a, and the light extraction structure 411 b are differentcomponents, but one embodiment of the present invention is not limitedto this structure. Two or all of these may be formed as one component.Furthermore, in the case where unevenness of the first electrode 421 isnot formed (for example, in the case where the light extractionstructure 411 b does not have unevenness) when the light extractionstructure 411 b is provided, the planarization layer 413 is notnecessarily provided.

Although the shape of the light-emitting device illustrated in FIG. 3Ais octagonal, one embodiment of the present invention is not limitedthereto. The shape of the light-emitting device may be another polygonalshape or a shape having a curved portion. As the shape of thelight-emitting device, a triangle, a quadrilateral, a hexagon, or thelike is especially preferred. This is because a plurality oflight-emitting devices having such a shape can be provided in a limitedarea without a gap. In addition, such light-emitting devices can beformed effectively utilizing a limited substrate area. Furthermore, thenumber of light-emitting elements included in the light-emitting deviceis not limited to one and may be more than one.

The shapes of the unevenness of the light extraction structure 411 a andthe light extraction structure 411 b do not necessarily have regularity.When the shape of the unevenness has regularity, the unevennessfunctions as a diffraction grating depending on the size of theunevenness, so that an interference effect is increased and light with acertain wavelength is easily extracted to the atmosphere in some cases.Therefore, it is preferable that the shape of the unevenness do not haveregularity.

There is no particular limitation on the base shape of the unevenness;for example, the shape may be a polygon such a triangle or a quadrangle,a circle, or the like. When the base shape of the unevenness has orderof regularity, the unevenness is preferably provided such that gaps arenot formed between adjacent portions of the unevenness. A regularhexagon is given as an example of a preferable base shape.

There is no particular limitation on the shape of the unevenness; forexample, a hemisphere or a shape with a vertex such as a circular cone,a pyramid (e.g., a triangular pyramid or a square pyramid), or anumbrella shape can be used.

In particular, the size or height of the unevenness is preferablygreater than or equal to 1 μm, in which case the influence ofinterference of light can be reduced.

The light extraction structure 411 a and the light extraction structure411 b can be formed directly on the support substrate 401. For example,any of the following methods can be used as appropriate: an etchingmethod, a sand blasting method, a microblast processing method, a frostprocessing method, a droplet discharge method, a printing method (screenprinting or offset printing by which a pattern is formed), a coatingmethod such as a spin coating method, a dipping method, a dispensermethod, an imprint method, and a nanoimprint method.

As a material of the light extraction structure 411 a and the lightextraction structure 411 b, a resin can be used, for example. As thelight extraction structure 411 a and the light extraction structure 411b, a hemispherical lens, a micro lens array, a film provided with anuneven structure, a light diffusing film, or the like can be used. Forexample, the above lens or film is attached onto the support substrate401 with the use of an adhesive whose refractive index is substantiallyequal to that of the support substrate 401 or the above lens or film, sothat the light extraction structure 411 a and the light extractionstructure 411 b can be formed.

The planarization layer 413 is more flat in its one surface that is incontact with the first electrode 421 than in its other surface that isin contact with the light extraction structure 411 b. Accordingly, thefirst electrode 421 can be a flat film. As a result, generation ofleakage current in the EL layer 423 due to unevenness of the firstelectrode 421 can be suppressed. As a material of the planarizationlayer 413, a glass, a liquid, a resin, or the like having a highrefractive index can be used. The planarization layer 413 has alight-transmitting property.

This embodiment can be combined with any of the other embodiments asappropriate.

Embodiment 5

In this embodiment, a light-emitting device of one embodiment of thepresent invention will be described with reference to FIGS. 4A and 4B.FIG. 4A is a plan view of the light-emitting device of one embodiment ofthe present invention and FIG. 4B is a cross-sectional view taken alonga dashed-dotted line C-D in FIG. 4A.

An active matrix light-emitting device according to this embodimentincludes, over a support substrate 501, a light-emitting portion 551, adriver circuit portion 552 (gate side driver circuit portion), a drivercircuit portion 553 (source side drive circuit portion), and the sealant507. The light-emitting portion 551, the driver circuit portions 552 and553 are formed in a space 515 formed by the support substrate 501, asealing substrate 505, and the sealant 507.

The light-emitting portion 551 illustrated in FIG. 4B includes aplurality of light-emitting units each including a switching transistor541 a, a current control transistor 541 b, and the second electrode 525electrically connected to a wiring (a source electrode or a drainelectrode) of the transistor 541 b.

A light-emitting element 503 has a top emission structure, and includesa first electrode 521 that transmits visible light, an EL layer 523, andthe second electrode 525 that reflects visible light. Further, apartition wall 519 is formed to cover an end portion of the secondelectrode 525.

One embodiment of the present invention is applied to the light-emittingelement 503. Specifically, a light-emitting layer included in the ELlayer 523 contains the organic compound of one embodiment of the presentinvention. Thus, the light-emitting element 503 has a long lifetime. Byapplication of one embodiment of the present invention, a highlyreliable light-emitting device can be achieved.

Over the support substrate 501, a lead wiring 517 for connecting anexternal input terminal through which a signal (e.g., a video signal, aclock signal, a start signal, or a reset signal) or a potential from theoutside is transmitted to the driver circuit portions 552 and 553 isprovided. Here, an example in which a flexible printed circuit (FPC) 509is provided as the external input terminal is described. Note that aprinted wiring board (PWB) may be attached to the FPC 509. In thisspecification, the light-emitting device includes in its category thelight-emitting device itself and the light-emitting device on which theFPC or the PWB is mounted.

The driver circuit portions 552 and 553 have a plurality of transistors.FIG. 4B illustrates an example in which the driver circuit portion 552has a CMOS circuit which is a combination of an n-channel transistor 542and a p-channel transistor 543. A circuit included in the driver circuitportion can be formed with various types of circuits such as a CMOScircuit, a PMOS circuit, or an NMOS circuit. The present invention isnot limited to a driver-integrated type described in this embodiment inwhich the driver circuit is formed over the substrate over which thelight-emitting portion is formed. The driver circuit can be formed overa substrate that is different from the substrate over which thelight-emitting portion is formed.

To prevent an increase in the number of manufacturing steps, the leadwiring 517 is preferably formed using the same material and the samestep(s) as those of the electrode or the wiring in the light-emittingportion or the driver circuit portion.

Described in this embodiment is an example in which the lead wiring 517is formed using the same material and the same step(s) as those of thesource electrode and the drain electrode of the transistor included inthe light-emitting portion 551 and the driver circuit portion 552.

In FIG. 4B, the sealant 507 is in contact with a first insulating layer511 over the lead wiring 517. The adhesion of the sealant 507 to metalis low in some cases. Therefore, the sealant 507 is preferably incontact with an inorganic insulating film over the lead wiring 517; sucha structure enables a light-emitting device with high sealing property,high adhesion property, and high reliability to be achieved. As examplesof the inorganic insulating film, an oxide film of a metal or asemiconductor, a nitride film of a metal or a semiconductor, and anoxynitride film of a metal or a semiconductor are given; specifically, asilicon oxide film, a silicon nitride film, a silicon oxynitride film, asilicon nitride oxide film, an aluminum oxide film, a titanium oxidefilm, and the like can be given.

The first insulating layer 511 has an effect of preventing diffusion ofimpurities into a semiconductor included in the transistor. As thesecond insulating layer 513, an insulating film with a planarizationfunction is preferably selected in order to reduce surface unevennessdue to the transistor.

There is no particular limitation on the structure of the transistorused in the light-emitting device of one embodiment of the presentinvention. A top-gate transistor may be used, or a bottom-gatetransistor such as an inverted staggered transistor may be used. Thetransistor may be a channel-etched transistor or a channel protectivetransistor. In addition, there is no particular limitation on a materialused for the transistor.

A semiconductor layer can be formed using silicon or an oxidesemiconductor. As a silicon semiconductor, single crystal silicon,polycrystalline silicon, or the like can be used as appropriate. As anoxide semiconductor, an In—Ga—Zn-based metal oxide or the like can beused as appropriate. Note that the semiconductor layer is preferablyformed using an oxide semiconductor which is an In—Ga—Zn-based metaloxide so that a transistor with low off-state current is achieved, inwhich case an off-state leakage current of the light-emitting elementcan be reduced.

A color filter 533 that is a coloring layer is provided on the sealingsubstrate 505 so as to overlap with the light-emitting element 503 (itslight-emitting region). The color filter 533 is provided to control thecolor of light emitted from the light-emitting element 503. For example,in a full-color display device using white light-emitting elements, aplurality of light-emitting units provided with color filters ofdifferent colors are used. In that case, three colors, red (R), green(G), and blue (B), may be used, or four colors, red (R), green (G), blue(B), and yellow (Y), may be used.

A black matrix 531 is provided between the adjacent color filters 533(in a position overlapping with the partition wall 519). The blackmatrix 531 shields a light-emitting unit from light emitted from thelight-emitting elements 503 in adjacent light-emitting units andprevents color mixture between the adjacent light-emitting units. Here,the color filter 533 is provided so that its end portions overlap withthe black matrix 531, whereby light leakage can be reduced. The blackmatrix 531 can be formed using a material that blocks light emitted fromthe light-emitting element 503; for example, a metal or a resin can beused. Note that the black matrix 531 may be provided in a region otherthan the light-emitting portion 551, for example, in the driver circuitportion 552.

An overcoat layer 535 is formed to cover the color filter 533 and theblack matrix 531. The overcoat layer 535 is formed using a material thattransmits light emitted from the light-emitting element 503; forexample, an inorganic insulating film or an organic insulating film canbe used. The overcoat layer 535 is not necessarily provided unlessneeded.

A structure of the present invention is not limited to thelight-emitting device using a color filter method, which is described asan example in this embodiment. For example, a separate coloring methodor a color conversion method may be used.

This embodiment can be combined with any of the other embodiments asappropriate.

Embodiment 6

In this embodiment, examples of electronic devices and lighting devicesusing a light-emitting device to which one embodiment of the presentinvention is applied will be described with reference to FIGS. 5A to 5Eand FIGS. 6A and 6B.

A light-emitting element containing the organic compound of oneembodiment of the present invention is applied to a light-emittingdevice used for electronic devices and lighting devices of thisembodiment; thus, the electronic devices and lighting devices have highreliability.

Examples of the electronic devices to which the light-emitting device isapplied are a television device (also referred to as television ortelevision receiver), a monitor of a computer or the like, a camera suchas a digital camera or a digital video camera, a digital photo frame, amobile phone (also referred to as cellular phone or cellular phonedevice), a portable game machine, a portable information terminal, anaudio reproducing device, a large-sized game machine such as a pachinkomachine, and the like. Specific examples of these electronic devices anda lighting device are illustrated in FIGS. 5A to 5E and FIGS. 6A and 6B.

FIG. 5A illustrates an example of a television device. In a televisiondevice 7100, a display portion 7102 is incorporated in a housing 7101.The display portion 7102 is capable of displaying images. Thelight-emitting device to which one embodiment of the present inventionis applied can be used for the display portion 7102. In addition, here,the housing 7101 is supported by a stand 7103.

Operation of the television device 7100 can be performed with anoperation switch of the housing 7101 or a separate remote controller7111. With operation keys of the remote controller 7111, channels andvolume can be controlled and images displayed on the display portion7102 can be controlled. Furthermore, the remote controller 7111 may beprovided with a display portion for displaying data output from theremote controller 7111.

Note that the television device 7100 is provided with a receiver, amodem, and the like. With the receiver, a general television broadcastcan be received. Furthermore, when the television device 7100 isconnected to a communication network by wired or wireless connection viathe modem, one-way (from a transmitter to a receiver) or two-way(between a transmitter and a receiver, between receivers, or the like)data communication can be performed.

FIG. 5B illustrates an example of a computer. A computer 7200 includes amain body 7201, a housing 7202, a display portion 7203, a keyboard 7204,an external connection port 7205, a pointing device 7206, and the like.Note that this computer is manufactured by using the light-emittingdevice of one embodiment of the present invention for the displayportion 7203.

FIG. 5C illustrates an example of a portable game machine. A portablegame machine 7300 includes two housings, a housing 7301 a and a housing7301 b, which are connected with a joint portion 7302 so that theportable game machine can be opened or folded. A display portion 7303 ais incorporated in the housing 7301 a and a display portion 7303 b isincorporated in the housing 7301 b. In addition, the portable gamemachine illustrated in FIG. 5C includes a speaker portion 7304, arecording medium insertion portion 7305, operation keys 7306, aconnection terminal 7307, a sensor 7308 (a sensor having a function ofmeasuring force, displacement, position, speed, acceleration, angularvelocity, rotational frequency, distance, light, liquid, magnetism,temperature, chemical substance, sound, time, hardness, electric field,current, voltage, electric power, radiation, flow rate, humidity,gradient, vibration, smell, or infrared ray), an LED lamp, a microphone,and the like. The structure of the portable game machine is not limitedto the above as long as the light-emitting device according to oneembodiment of the present invention is used for at least either thedisplay portion 7303 a or the display portion 7303 b, or both of them.The portable game machine may be provided with other accessories asappropriate. The portable game machine illustrated in FIG. 5C has afunction of reading a program or data stored in a recording medium todisplay it on the display portion, and a function of sharing data withanother portable game machine by wireless communication. Note that afunction of the portable game machine illustrated in FIG. 5C is notlimited to the above, and the portable game machine can have a varietyof functions.

FIG. 5D illustrates an example of a mobile phone. A mobile phone 7400 isprovided with a display portion 7402 incorporated in a housing 7401,operation buttons 7403, an external connection port 7404, a speaker7405, a microphone 7406, and the like. Note that the mobile phone 7400is manufactured using the light-emitting device of one embodiment of thepresent invention for the display portion 7402. A highly reliable mobilephone can be obtained by using the light-emitting device of oneembodiment of the present invention for the display portion 7402.

When the display portion 7402 of the mobile phone 7400 illustrated inFIG. 5D is touched with a finger or the like, data can be input into themobile phone 7400. Further, operations such as making a call andcomposing an e-mail can be performed by touching the display portion7402 with a finger or the like.

There are mainly three screen modes of the display portion 7402. Thefirst mode is a display mode mainly for displaying images. The secondmode is an input mode mainly for inputting data such as text. The thirdmode is a display-and-input mode in which two modes of the display modeand the input mode are combined.

For example, in the case of making a call or composing an e-mail, a textinput mode mainly for inputting text is selected for the display portion7402 so that text displayed on the screen can be inputted.

When a detection device including a sensor for detecting inclination,such as a gyroscope or an acceleration sensor, is provided inside themobile phone 7400, display on the screen of the display portion 7402 canbe automatically switched by determining the orientation of the mobilephone 7400 (whether the mobile phone is placed horizontally orvertically for a landscape mode or a portrait mode).

The screen modes are switched by touching the display portion 7402 oroperating the operation buttons 7403 of the housing 7401. The screenmodes can also be switched depending on the kind of image displayed onthe display portion 7402. For example, when a signal of an imagedisplayed on the display portion is a signal of moving image data, thescreen mode is switched to the display mode. When the signal is a signalof text data, the screen mode is switched to the input mode.

Moreover, in the input mode, when input by touching the display portion7402 is not performed for a certain period while a signal detected by anoptical sensor in the display portion 7402 is detected, the screen modemay be controlled so as to be switched from the input mode to thedisplay mode.

The display portion 7402 may function as an image sensor. For example,an image of a palm print, a fingerprint, or the like is taken when thedisplay portion 7402 is touched with the palm or the finger, wherebypersonal authentication can be performed. Further, by providing abacklight or a sensing light source which emits near-infrared light inthe display portion, an image of a finger vein, a palm vein, or the likecan be taken.

FIG. 5E illustrates an example of a fordable tablet terminal (in an openstate). A tablet terminal 7500 includes a housing 7501 a, a housing 7501b, a display portion 7502 a, and a display portion 7502 b. The housing7501 a and the housing 7501 b are connected by a hinge 7503 and can beopened and closed along the hinge 7503. The housing 7501 a includes apower switch 7504, operation keys 7505, a speaker 7506, and the like.Note that the tablet terminal 7500 is manufactured using thelight-emitting device of one embodiment of the present invention foreither the display portion 7502 a or the display portion 7502 b or both.

Part of the display portion 7502 a or the display portion 7502 b can beused as a touch panel region, and data can be input by touchingdisplayed operation keys. For example, the entire area of the displayportion 7502 a can display keyboard buttons and serve as a touch panelwhile the display portion 7502 b can be used as a display screen.

FIG. 6A illustrates a desk lamp including a lighting portion 7601, ashade 7602, an adjustable arm 7603, a support 7604, a base 7605, and apower switch 7606. The desk lamp is manufactured using thelight-emitting device of one embodiment of the present invention for thelighting portion 7601. Note that a lamp includes a ceiling light, a walllight, and the like in its category.

FIG. 6B illustrates an example in which the light-emitting device of oneembodiment of the present invention is used for an indoor lightingdevice 7701. Since the light-emitting device of one embodiment of thepresent invention can have a larger area, it can be used as a large-arealighting device. In addition, the light-emitting device can be used as aroll-type lighting device 7702. As illustrated in FIG. 6B, a desk lamp7703 described with reference to FIG. 6A may be used in a room providedwith the indoor lighting device 7701.

Example 1 Synthesis Example 1

In this example, a description will be made of a method of synthesizing9,9-dimethyl-N-[4-(1-naphthyl)phenyl]-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9H-fluoren-2-amine(abbreviation: PCBNBF) represented by Structural Formula (100) shownbelow.

In this example, two methods of synthesizing PCBNBF will be described.

Synthesis Method 1 Step 1-1: Synthesis of 1-(4-bromophenyl)naphthalene

Synthesis Scheme (a-1) of Step 1-1 is shown.

Into a 3-L three-neck flask were put 47 g (0.28 mol) of1-naphthaleneboronic acid and 82 g (0.29 mol) of 4-bromoiodobenzene, and750 mL of toluene and 250 mL of ethanol were added thereto. While thepressure was reduced, this mixture was degassed by being stirred. Afterthe degassing, the atmosphere in the flask was replaced with nitrogen.To the solution was added 415 mL (2.0 mol/L) of a potassium carbonatesolution. The obtained mixture was degassed by being stirred while thepressure was reduced, and then, the atmosphere in the flask was replacedwith nitrogen. Into this were added 4.2 g (14 mmol) oftris(2-methylphenyl)phosphine and 0.7 g (2.8 mmol) of palladium(II)acetate. This mixture was stirred under a nitrogen stream at 90° C. foran hour.

After the stirring, this mixture was allowed to cool to roomtemperature, and an aqueous layer of this mixture was extracted threetimes with toluene. The extracted solution and an organic layer werecombined and washed twice with water and washed twice with saturatedsaline. Into this mixture was added magnesium sulfate, and the mixturewas dried for 18 hours. The obtained mixture was subjected to naturalfiltration to remove magnesium sulfate, and the filtrate wasconcentrated to obtain an orange liquid.

To this orange liquid was added 500 mL of hexane, and the obtainedsolution was filtrated through Celite (produced by Wako Pure ChemicalIndustries, Ltd., Catalog No. 531-16855, the same applies to Celitedescribed below and a repetitive description thereof is omitted) andFlorisil (produced by Wako Pure Chemical Industries, Ltd., Catalog No.540-00135, the same applies to Florisil described below and a repetitivedescription thereof is omitted). The obtained filtrate was concentratedto give a colorless liquid. Into the colorless liquid was added hexane,the obtained mixture was kept at −10° C., and a precipitated impuritywas separated by filtration. The obtained filtrate was concentrated togive a colorless liquid. This colorless liquid was purified bydistillation under reduced pressure to give a yellow liquid, and theyellow liquid was purified by silica gel column chromatography(developing solvent: hexane), whereby 56 g of an objective colorlessliquid was obtained in a yield of 72%.

Step 1-2: Synthesis of9,9-dimethyl-N-(4-naphthyl)phenyl-N-phenyl-9H-fluoren-2-amine

Synthesis Scheme (a-2) of Step 1-2 is shown.

Into a 1-L three-neck flask were put 40 g (0.14 mol) of9,9-dimethyl-N-phenyl-9H-fluoren-2-amine, 40 g (0.42 mol) of sodiumtert-butoxide, and 2.8 g (1.4 mmol) ofbis(dibenzylideneacetone)palladium(0), and 560 mL of a toluene solutioncontaining 44 g (0.15 mol) of 1-(4-bromophenyl)naphthalene was addedthereto. This mixture was degassed by being stirred while the pressurewas reduced. After the degassing, the atmosphere in the flask wasreplaced with nitrogen. Then, 14 mL (7.0 mmol) oftri(tert-butyl)phosphine (a 10 wt % hexane solution) was added, and theobtained mixture was stirred under a nitrogen stream at 110° C. for twohours.

The mixture was cooled to room temperature, and a solid was separated bysuction filtration. The obtained filtrate was concentrated to give adark brown liquid. The dark brown liquid and toluene were combined, andthe obtained solution was filtrated through Celite, alumina, andFlorisil. The obtained filtrate was concentrated to give a light yellowliquid. The light yellow liquid was recrystallized from acetonitrile,whereby 53 g of an objective light yellow powder was obtained in a yieldof 78%.

Step 1-3: Synthesis ofN-(4-bromophenyl)-9,9-dimethyl-N-[4-(1-naphthyl)phenyl]-9H-fluoren-2-amine

Synthesis Scheme (a-3) of Step 1-3 is shown.

Into a 2-L Meyer flask were put 59 g (0.12 mol) of9,9-dimethyl-N-(4-naphthyl)phenyl-N-phenyl-9H-fluoren-2-amine and 300 mLof toluene, and the mixture was stirred while being heated. The obtainedsolution was allowed to cool to room temperature, and 300 mL of ethylacetate was added thereto. To this mixture was added 21 g (0.12 mol) ofN-bromosuccinimide (abbreviation: NBS), and the obtained mixture wasstirred at room temperature for about 2.5 hours. To this mixture wasadded 400 mL of a saturated aqueous solution of sodium hydrogencarbonate, and the mixture was stirred at room temperature. An organiclayer of this mixture was washed twice with a saturated aqueous solutionof sodium hydrogen carbonate, and washed twice with saturated saline.Then, magnesium sulfate was added thereto and the mixture was dried fortwo hours. The obtained mixture was subjected to natural filtration toremove magnesium sulfate, and the filtrate was concentrated to give ayellow liquid. This liquid was dissolved in toluene, and the obtainedsolution was filtrated through Celite, alumina, and Florisil, whereby alight yellow solid was obtained. The obtained light yellow solid wasreprecipitated from toluene/acetonitrile, whereby 56 g of an objectivewhite powder was obtained in a yield of 85%.

Step 1-4: Synthesis of PCBNBF

Synthesis Scheme (a-4) of Step 1-4 is shown.

Into a 1-L three-neck flask were put 51 g (90 mmol) ofN-(4-bromophenyl)-9,9-dimethyl-N-[4-(1-naphthyl)phenyl]-9H-fluoren-2-amine,28 g (95 mmol) of 9-phenyl-9H-carbazole-3-boronic acid, 0.4 mg (1.8mmol) of palladium(II) acetate, 1.4 g (4.5 mmol) oftri(o-tolyl)phosphine, 300 mL of toluene, 100 mL of ethanol, and 135 mL(2.0 mol/L) of a potassium carbonate solution. The mixture was degassedby being stirred while the pressure was reduced. After the degassing,the atmosphere in the flask was replaced with nitrogen. The mixture wasstirred under a nitrogen stream at 90° C. for 1.5 hours. After thestirring, the mixture was allowed to cool to room temperature, and theprecipitated solid was collected by suction filtration. An organic layerwas extracted from the obtained mixture of an aqueous layer and theorganic layer, and the organic layer was concentrated to give a brownsolid. The brown solid was recrystallized from toluene/ethylacetate/ethanol, whereby an objective white powder was obtained. Thesolid collected after the stirring and the white powder obtained by therecrystallization were dissolved in toluene, and then filtrated throughCelite, alumina, and Florisil. The obtained solution was concentratedand recrystallized from toluene/ethanol, whereby 54 g of an objectivewhite powder was obtained in a yield of 82%.

By a train sublimation method, 51 g of the obtained white powder waspurified by sublimation. In the purification by sublimation, the whitepowder was heated at 360° C. under a pressure of 3.7 Pa with a flow rateof argon gas of 15 mL/min. After the purification by sublimation, 19 gof an objective light yellow solid was obtained at a collection rate of38%.

By a nuclear magnetic resonance (NMR) method, this compound wasidentified as9,9-dimethyl-N-[4-(1-naphthyl)phenyl]-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9H-fluoren-2-amine(abbreviation: PCBNBF), which was an objective substance.

¹H NMR data of the obtained substance are as follows: ¹H NMR (CDCl₃, 500MHz): δ=1.50 (s, 6H), 7.21 (dd, J=8.0 Hz, 1.6 Hz, 1H), 7.26-7.38 (m,8H), 7.41-7.44 (m, 5H), 7.46-7.55 (m, 6H), 7.59-7.69 (m, 9H), 7.85 (d,J=8.0 Hz, 1H), 7.91 (dd, J=7.5 Hz, 1.7 Hz, 1H), 8.07-8.09 (m, 1H), 8.19(d, J=8.0 Hz, 1H), 8.37 (d, J=1.7 Hz, 1H).

The ¹H-NMR chart is shown in FIGS. 7A and 7B. Note that FIG. 7B is achart showing an enlarged part of FIG. 7A in the range of 7.00 ppm to10.0 ppm.

Synthesis Method 2 Step 2-1: Synthesis of 1-(4-aminophenyl)naphthalene

Synthesis Scheme (b-1) of Step 2-1 is shown.

Into a 2-L three-neck flask were put 25 g (0.15 mol) of 4-bromoaniline,25 g (0.15 mol) of 1-naphthaleneboronic acid, 450 mL of toluene, and 150mL of ethanol. While the pressure was reduced, this mixture was degassedby being stirred. After the degassing, the atmosphere in a system wasreplaced with nitrogen. Into the solution was added 220 mL (2.0 mol/L)of a potassium carbonate solution. The obtained mixture was degassed bybeing stirred while the pressure was reduced, and then, the atmospherein the system was replaced with nitrogen. To this mixture were added0.48 g (2.1 mmol) of palladium(II) acetate and 2.4 g (7.9 mmol) oftris(2-methylphenyl)phosphine, and the obtained mixture was stirredunder a nitrogen stream at 80° C. for three hours. After the stirring,this mixture was allowed to cool to room temperature, and an aqueouslayer of this mixture was extracted three times with toluene. Theextracted solution and an organic layer were combined and washed twicewith water and washed twice with saturated saline. Into this mixture wasadded magnesium sulfate, and the mixture was dried for 18 hours. Theobtained mixture was subjected to natural filtration to remove magnesiumsulfate, and the filtrate was concentrated to obtain an orange liquid.This orange liquid was dissolved in toluene, and this solution wasfiltrated through Celite, alumina, and Florisil. The obtained filtratewas concentrated to give 33 g of an objective orange liquid in a yieldof 99%.

Step 2-2: Synthesis of4-(1-naphthyl)-4-(9-phenyl-9H-carbazol-3-yl)diphenylamine

Synthesis Scheme (b-2) of Step 2-2 is shown.

Into a 2-L three-neck flask were put 50 g (0.13 mol) of3-(4-bromopheny)-9-phenyl-9H-carbazole, 36 g (0.38 mol) of sodiumtert-butoxide, 30 g (0.14 mol) of 4-(1-naphthyl)aniline, and 500 mL oftoluene. This mixture was degassed by being stirred while the pressurein a system was reduced. After the degassing, the atmosphere in thesystem was replaced with nitrogen. Then, into this mixture was added0.79 g (1.4 mmol) of bis(dibenzylideneacetone)palladium(0) and 13 mL oftri(tert-butyl)phosphine (a 10 wt % hexane solution), and the obtainedmixture was stirred at 80° C. for about two hours, and then stirred at110° C. for three hours. After the stirring, 0.39 g (0.68 mmol) ofbis(dibenzylideneacetone)palladium(0) and 4.5 mL oftri(tert-butyl)phosphine (a 10 wt % hexane solution) were added, and theobtained mixture was stirred at 110° C. for three hours. After theheating, the mixture was cooled down to room temperature while beingstirred, and was subjected to suction filtration so as to separate asolid. The obtained filtrate was concentrated. The obtained solution wasdissolved in toluene, and this solution was filtrated through Celite,alumina, and Florisil. A liquid obtained by concentrating the solutionwas recrystallized from hexane, whereby a black solid was obtained.

The black solid was desolved in toluene, and the solution was washedthree times with water and washed twice with saturated saline. Magnesiumsulfate was added to the organic layer to dry the organic layer, and themixture was naturally filtered to remove the magnesium sulfate. Theobtained filtrate was filtrated through Celite, alumina, and Florisil.The obtained solution was concentrated to give a yellow liquid. Thisyellow liquid was recrystallized from hexane to give a yellow powder.This yellow powder was suspended in toluene and the resulting mixturewas washed by ultrasonic irradiation, whereby 18 g of an objective lightyellow powder was obtained in a yield of 27%. The filtrate obtained bythe recrystallization and the filtrate resulted from the filtration bythe ultrasonic wave irradiation were combined, and then purified bysilica gel column chromatography (the ratio of hexane to toluene in adeveloping solvent was gradually changed from 4:1 to 2:3), whereby ayellow solid was obtained. This yellow solid was recrystallized fromtoluene, whereby 12 g of an objective light yellow powder was obtainedin a yield of 18%. In total, 30 g of the objective light yellow powderwas obtained in a yield of 45%. In addition, the filtrate obtained afterthe recrystallization was concentrated to give 26 g of a yellow solidcontaining the objective substance.

By a train sublimation method, 22 g of the yellow solid, which wasobtained by concentration after the recrystallization, was subjected topurification by sublimation. The purification by sublimation wasconducted by heating the yellow solid at 305° C. under a pressure of 2.9Pa with a flow rate of argon gas of 10 mL/min. After the purification bysublimation, 7.1 g of a light yellow solid was obtained at a collectionrate of 38%.

By a train sublimation method, 7.1 g of the light yellow solid, whichwas obtained by the purification by sublimation, was purified bysublimation. The purification by sublimation was conducted by heating ofthe light yellow solid at 305° C. under a pressure of 2.2 Pa with a flowrate of argon gas of 10 mL/min. After the purification by sublimation,5.7 g of an objective light yellow solid was obtained at a collectionrate of 80%.

Step 2-3: Synthesis of PCBNBF

Synthesis Scheme (b-3) of Step 2-3 is shown.

Into a 100-mL three-neck flask were put 4.7 g (8.8 mmol) of4-(1-naphthyl)-4′-(9-phenyl-9H-carbazol-3-yl)diphenylamine, 2.6 g (27mmol) of sodium tert-butoxide, 0.17 g (0.17 mmol) ofbis(dibenzylideneacetone)palladium(0), and a solution obtained bydissolving 2.3 g (8.1 mmol) of 2-bromo-9,9′-dimethyl-9H-fluorene in 40mL of toluene. This mixture was degassed by being stirred while thepressure in a system was reduced, and the atmosphere in the system wasreplaced with nitrogen. After the degassing, 0.8 mL oftri(tert-butyl)phosphine (a 10 wt % hexane solution) was added to thismixture, and the mixture was refluxed at 110° C. for two hours. Afterthe reflux, the mixture was allowed to cool to room temperature, andfiltered through Celite to remove a solid. The obtained filtrate wasfiltrated through Celite, alumina, and Florisil, whereby an objectivelight yellow solid was obtained.

This light yellow solid was recrystallized from toluene/ethanol, so that1.4 g of an objective white powder was obtained. Mother liquor obtainedby the recrystalization was concentrated, and a resulting white solidwas recrystallized from ethyl acetate/acetonitrile, whereby 2.2 g of anobjective white powder was obtained. The total amount of the objectivewhite powder including the one collected in the previous step was 3.6 gand the yield was 59%.

By a train sublimation method, 3.6 g of the obtained white powder waspurified by sublimation. In the purification by sublimation, the whitepowder was heated at 370° C. under a pressure of 3.7 Pa with a flow rateof argon gas of 15 mL/min. After the purification by sublimation, 2.0 gof an objective light yellow solid was obtained at a collection rate of56%.

By a nuclear magnetic resonance (NMR) method, this compound wasidentified as PCBNBF, which was an objective substance. Note that ¹H NMRdata of the obtained substance were similar to those of the substanceobtained by Synthesis Method 1.

In Synthesis Method 2 described in this example, the yield of4-(1-naphthyl)-4′-(9-phenyl-9H-carbazol-3-yl)diphenylamine (hereinafterreferred to as an objective substance A), which is the objectivesubstance in Step 2-2, was low. This is because4-(1-naphthyl)-4′,4″-bis(9-phenyl-9H-carbazol-3-yl)triphenylamine(hereinafter referred to as a by-product B), which is a compoundrepresented by Structural Formula (900), was generated as a by-product.

The by-product B has solubility and polarity that are very similar tothose of the objective substance A; thus, it was difficult to remove theby-product B by recrystlization or a purification method such as columnchromatography.

Here, the by-product B has an extra substituent including a carbazolylgroup in comparison with the objective substance A; thus, thermophysicalproperty of the by-product B is higher than that of the objectivesubstance A. For this reason, when purification by sublimation wasperformed by a train sublimation method to obtain the objectivesubstance A, the by-product B was able to be removed easily.

Note that in the case where synthesis of Step 2-3 is performed using theobjective substance A containing a small amount of the by-product B, itis difficult to remove the by-product B by recrystlization or apurification method such as column chromatography because the by-productB has solubility and polarity that are very similar to those of PCBNBFthat is the objective substance in Step 2-3. In addition, the molecularweight of the by-product B is close to that of PCBNBF; thus, it isdifficult to remove the by-product B by purification by sublimation.Therefore, in the case where PCBNBF is synthesized by Synthesis Method2, the objective substance A needs to be highly purified.

Accordingly, Synthesis Method 1 is applied to synthesis of PCBNBF, whichis an objective substance, in order to highly purify the objectivesubstance A, so that the objective substance A can be obtained withoutgenerating the by-product B. Therefore, Synthesis Method 1 is preferredas the method of synthesizing PCBNBF.

FIG. 8A shows the absorption spectrum of PCBNBF in a toluene solution ofPCBNBF, and FIG. 8B shows the emission spectrum thereof. FIG. 9A showsthe absorption spectrum of a thin film of PCBNBF, and FIG. 9B shows anemission spectrum thereof. The absorption spectrum was measured with aUV-visible spectrophotometer (V-550, manufactured by JASCO Corporation).The measurements were performed with samples prepared in such a mannerthat the solution was put in a quartz cell and the thin film wasobtained by evaporation onto a quartz substrate. The absorption spectrumof the solution was obtained by subtracting the absorption spectra ofquartz and toluene from those of quartz and the solution, and theabsorption spectrum of the thin film was obtained by subtracting theabsorption spectrum of a quartz substrate from those of the quartzsubstrate and the thin film. In FIGS. 8A and 8B and

FIGS. 9A and 9B, the horizontal axis represents wavelength (nm) and thevertical axis represents intensity (arbitrary unit). In the case of thetoluene solution, an absorption peak is observed at around 352 nm, andan emission wavelength peak is observed at 417 nm (an excitationwavelength of 352 nm). In the case of the thin film, absorption peaksare observed at around 212 nm, 283 nm, and 358 nm, and an emissionwavelength peak is observed at 434 nm (an excitation wavelength of 371nm).

Furthermore, mass spectrometry (MS) of PCBNBF was conducted by liquidchromatography mass spectrometry (LC/MS).

The analysis by LC/MS was carried out with Acquity UPLC (manufactured byWaters Corporation) and Xevo G2 Tof MS (manufactured by WatersCorporation). In the MS, ionization was carried out by an electrosprayionization (ESI) method. At this time, the capillary voltage and thesample cone voltage were set to 3.0 kV and 30 V, respectively, anddetection was performed in a positive mode. A component which underwentthe ionization under the above conditions was collided with an argon gasin a collision cell to dissociate into product ions. Energy (collisionenergy) for the collision with argon was 50 eV and 70 eV. A mass rangefor the measurement was m/z 100-1200. FIG. 22A shows the measurementresults in the case of a collision energy of 50 eV. FIG. 22B shows themeasurement results in the case of a collision energy of 70 eV.

The results in FIG. 22A show that, owing to the presence and absence ofhydrogen ions and isotopes, a plurality of product ions of PCBNBF aredetected mainly around m/z 728, m/z 713, m/z 698, m/z 509, m/z 394, andm/z 294 in the case of a collision energy of 50 eV.

The results in FIG. 22B show that, owing to the presence and absence ofhydrogen ions and isotopes, a plurality of product ions of PCBNBF aredetected mainly around m/z 711, m/z 697, m/z 571, m/z 509, m/z 393, andm/z 256 in the case of a collision energy of 70 eV. The results in FIGS.22A and 22B are characteristically derived from PCBNBF and thus can beregarded as important data in identification of PCBNBF contained in amixture.

Example 2 Synthesis Example 2

In this example, a description will be made of a method of synthesizingN-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-N-[4-(1-naphthyl)phenyl]-9,9′-spirobi[9H-fluoren]-2-amine(abbreviation: PCBNBSF) represented by Structural Formula (101) shownbelow.

Synthesis Scheme (c-1) of PCBNBSF is shown.

Into a 1-L three-neck flask were put 33 g (62 mmol) of4-(1-naphthyl)-4′-(9-phenyl-9H-carbazol-3-yl)diphenylamine, 23 g (59mmol) of 2-bromo-9,9′-spirobi[9H-fluorene], 17 g (180 mmol) of sodiumtert-butoxide, and 235 mL of toluene. The mixture was degassed by beingstirred while the pressure was reduced and then, the atmosphere in theflask was replaced with nitrogen. To the mixture were added 1.5 mL (3.0mmol) of tri(tert-butyl)phosphine (a 10 wt % hexane solution) and 0.34 g(0.59 mmol) of bis(dibenzylideneacetone)palladium(0). The obtainedmixture was stirred under a nitrogen stream at 80° C. for two hours.After the stirring, this mixture was cooled down to room temperature,and the precipitated solid was separated by suction filtration. Theobtained filtrate was dissolved in toluene, and this solution wasfiltrated through Celite and Florisil. The obtained solution wasconcentrated to give a yellow solid. The yellow solid was recrystallizedfrom ethyl acetate/hexane, so that 47 g of an objective light yellowpowder was obtained in a yield of 94%. Note that Example 1 can bereferred to for the method of synthesizing4-(1-naphthyl)-4′-(9-phenyl-9H-carbazol-3-yl)diphenylamine.

By a train sublimation method, 7.4 g of the obtained light yellow powderwas purified by sublimation. In the purification by sublimation, thelight yellow powder was heated at 380° C. under a pressure of 3.6 Pawith a flow rate of argon gas of 15 mL/min. After the purification bysublimation, 6.1 g of a light yellow solid was obtained at a collectionrate of 82%.

By a train sublimation method, 6.1 g of the light yellow solid, whichwas obtained by the purification by sublimation, was purified bysublimation. The purification by sublimation was conducted by heating ofthe light yellow solid at 380° C. under a pressure of 3.6 Pa with a flowrate of argon gas of 15 mL/min. After the purification by sublimation,5.1 g of an objective light yellow solid was obtained at a collectionrate of 83%.

By a nuclear magnetic resonance (NMR) method, this compound wasidentified asN-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-N-[4-(1-naphthyl)phenyl]-9,9′-spirobi[9H-fluoren]-2-amine(abbreviation: PCBNBSF), which was an objective substance.

¹H NMR data of the obtained substance are as follows: ¹H NMR (CDCl₃, 500MHz): δ=6.69-6.71 (m, 2H), 6.85 (d, J=7.5 Hz, 2H), 7.06 (t, J=7.5 Hz,1H), 7.09-7.17 (m, 6H), 7.20 (dd, J=8.0 Hz, 2.3 Hz, 1H), 7.27-7.54 (m,16H), 7.58-7.63 (m, 5H), 7.74-7.83 (m, 5H), 7.88-7.93 (m, 2H), 8.17 (d,J=7.5 Hz, 1H), 8.28 (d, J=1.7 Hz, 1H).

The ¹H-NMR chart is shown in FIGS. 10A and 10B. Note that FIG. 10B is achart showing an enlarged part of FIG. 10A in the range of 6.00 ppm to10.0 ppm.

FIG. 11A shows the absorption spectrum of PCBNBSF in a toluene solutionof PCBNBSF, and FIG. 11B shows the emission spectrum thereof. FIG. 12Ashows the absorption spectrum of a thin film of PCBNBSF, and FIG. 12Bshows an emission spectrum thereof. The absorption spectra were measuredin the same manner as Example 1. In FIGS. 11A and 11B and FIGS. 12A and12B, the horizontal axis represents wavelength (nm) and the verticalaxis represents intensity (arbitrary unit). In the case of the toluenesolution, an absorption peak is observed at around 351 nm, and anemission wavelength peak is observed at 411 nm (an excitation wavelengthof 331 nm). In the case of the thin film, an absorption peak is observedat around 366 nm, and an emission wavelength peak is observed at 435 nm(an excitation wavelength of 375 nm).

Furthermore, mass spectrometry (MS) of PCBNBSF was conducted by liquidchromatography mass spectrometry (LC/MS).

Methods, conditions, and the like for the analysis by LC/MS were thesame as those in Example 1. Energy (collision energy) for the collisionwith argon was 70 eV. A mass range for the measurement was m/z 100-1200.FIGS. 23A and 23B show the measurement results.

The results in FIGS. 23A and 23B show that, owing to the presence andabsence of hydrogen ions and isotopes, a plurality of product ions ofPCBNBSF are detected mainly around m/z 851, m/z 648, m/z 536, m/z 333,and m/z 315. The results in FIGS. 23A and 23B are characteristicallyderived from PCBNBSF and thus can be regarded as important data inidentification of PCBNBSF contained in a mixture.

Example 3

In this example, a light-emitting element of one embodiment of thepresent invention will be described with reference to FIG. 13. Chemicalformulae of materials used in this example are shown below.

Methods of manufacturing a light-emitting element 1, a comparativelight-emitting element 2, and a comparative light-emitting element 3 ofthis example will be described below.

(Light-Emitting Element 1)

First, indium tin oxide containing silicon oxide (ITSO) was depositedover a glass substrate 1100 by a sputtering method, whereby a firstelectrode 1101 was formed. The thickness was 110 nm and the electrodearea was 2 mm×2 mm. Here, the first electrode 1101 functions as an anodeof the light-emitting element.

Next, as pretreatment for forming the light-emitting element over theglass substrate 1100, the surface of the substrate was washed withwater, baked at 200° C. for one hour, and subjected to UV ozonetreatment for 370 seconds.

After that, the glass substrate 1100 was transferred into a vacuumevaporation apparatus where the pressure had been reduced toapproximately 10⁻⁴ Pa, and subjected to vacuum baking at 170° C. for 30minutes in a heating chamber of the vacuum evaporation apparatus. Then,the glass substrate 1100 was allowed to cool for about 30 minutes.

Next, the glass substrate 1100 provided with the first electrode 1101was fixed to a substrate holder in the vacuum evaporation apparatus sothat a surface on which the first electrode 1101 was provided faceddownward. The pressure in the vacuum evaporation apparatus was reducedto about 10⁻⁴ Pa. Then,4,4′,4″-(1,3,5-benzenetriyl)tri(dibenzothiophene) (abbreviation:DBT3P-II) and molybdenum(VI) oxide were co-evaporated by an evaporationmethod using resistance heating to form a hole-injection layer 1111 onthe first electrode 1101. The thickness of the hole-injection layer 1111was set to 40 nm, and the weight ratio of DBT3P-II to molybdenum oxidewas adjusted to 4:2 (=DBT3P-II: molybdenum oxide). Note that theco-evaporation method refers to an evaporation method in whichevaporation is carried out from a plurality of evaporation sources atthe same time in one treatment chamber.

Next, 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation:BPAFLP) was deposited to a thickness of 20 nm over the hole-injectionlayer 1111, whereby a hole-transport layer 1112 was formed.

A light-emitting layer 1113 was formed over the hole-transport layer1112 by co-evaporation of 4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine(abbreviation: 4,6mDBTP2Pm-II),N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-N-[4-(1-naphthyl)phenyl]-9,9′-spirobi[9H-fluoren]-2-amine(abbreviation: PCBNBSF), and(acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(tBuppm)₂(acac)]). Here, a 15-nm-thick layer and a25-nm-thick layer were stacked. The 15-nm-thick layer was formed withthe weight ratio of 4,6mDBTP2Pm-II to PCBNBSF to [Ir(tBuppm)₂(acac)]adjusted to 0.7:0.3:0.05 (=4,6mDBTP2Pm-II: PCBNBSF:[Ir(tBuppm)₂(acac)]). The 25-nm-thick layer was formed with the weightratio of 4,6mDBTP2Pm-II to PCBNBSF to [Ir(tBuppm)₂(acac)] adjusted to0.8:0.2:0.05 (=4,6mDBTP2Pm-II: PCBNBSF: [Ir(tBuppm)₂(acac)]).

Next, over the light-emitting layer 1113, 4,6mDBTP2Pm-II was depositedto a thickness of 10 nm and then bathophenanthroline (abbreviation:BPhen) was deposited to a thickness of 20 nm, so that anelectron-transport layer 1114 was formed.

Further, a 1-nm-thick film of lithium fluoride (LiF) was formed over theelectron-transport layer 1114 by evaporation, whereby anelectron-injection layer 1115 was formed.

Lastly, a 200-nm-thick film of aluminum was formed by evaporation toform a second electrode 1103 functioning as a cathode. Thus, thelight-emitting element 1 of this example was manufactured.

Note that, in the above evaporation process, evaporation was allperformed by a resistance heating method.

(Comparative Light-Emitting Element 2)

The light-emitting layer 1113 of the comparative light-emitting element2 was formed by co-evaporation of 4,6mDBTP2Pm-II,4-phenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation:PCBA1BP), and [Ir(tBuppm)₂(acac)]. Here, a 15-nm-thick layer formed withthe weight ratio of 4,6mDBTP2Pm-II to PCBA1BP to [Ir(tBuppm)₂(acac)]adjusted to 0.7:0.3:0.05 (=4,6mDBTP2Pm-II: PCBA1BP: [Ir(tBuppm)₂(acac)])and a 25-nm-thick layer formed with the weight ratio of 4,6mDBTP2Pm-IIto PCBA1BP to [Ir(tBuppm)₂(acac)] adjusted to 0.8:0.2:0.05(=4,6mDBTP2Pm-II: PCBA1BP: [Ir(tBuppm)₂(acac)]) were stacked. The layersother than the light-emitting layer 1113 were formed in the same manneras those in the light-emitting element 1.

(Comparative Light-Emitting Element 3)

The light-emitting layer 1113 of the comparative light-emitting element3 was formed by co-evaporation of 4,6mDBTP2Pm-II,N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9′-bifluoren-2-amine(abbreviation: PCBASF), and [Ir(tBuppm)₂(acac)]. Here, a 15-nm-thicklayer formed with the weight ratio of 4,6mDBTP2Pm-II to PCBASF to[Ir(tBuppm)₂(acac)] adjusted to 0.7:0.3:0.05 (=4,6mDBTP2Pm-II: PCBASF:[Ir(tBuppm)₂(acac)]) and a 25-nm-thick layer formed with the weightratio of 4,6mDBTP2Pm-II to PCBASF to [Ir(tBuppm)₂(acac)] adjusted to0.8:0.2:0.05 (=4,6mDBTP2Pm-II: PCBASF: [Ir(tBuppm)₂(acac)]) werestacked. The layers other than the light-emitting layer 1113 were formedin the same manner as those in the light-emitting element 1.

Table 1 shows the element structures of the light-emitting elements ofthis example, which were manufactured in the above manner.

TABLE 1 first hole injection hole-transport light-emittingelectron-transport electron injection second electrode layer layer layerlayer layer electrode light-emitting ITSO DBT3P-II:MoOx BPAFLP4,6mDBTP2Pm-II:PCBNBSF: 4,6mDBT BPhen LiF Al element 1 110 nm (=4:3) 20nm [Ir(tBuppm)₂(acac)] P2Pm-II 20 nm 1 nm 200 nm 40 nm (=0.7:0.3:0.05)(=0.8:0.2:0.05) 10 nm 15 nm 25 nm comparative 4,6mDBTP2Pm-II:PCBA1BP:light-emitting [Ir(tBuppm)₂(acac)] element 2 (=0.7:0.3:0.05)(=0.8:0.2:0.05) 15 nm 25 nm comparative 4,6mDBTP2Pm-II:PCBASF:light-emitting [Ir(tBuppm)₂(acac)] element 3 (=0.7:0.3:0.05)(=0.8:0.2:0.05) 15 nm 25 nm

In a glove box containing a nitrogen atmosphere, each of thelight-emitting element 1, the comparative light-emitting element 2, andthe comparative light-emitting element 3 was sealed with a glasssubstrate so as not to be exposed to the air. Then, operationcharacteristics of these light-emitting elements were measured. Notethat the measurement was carried out at room temperature (in anatmosphere kept at 25° C.).

FIG. 14 shows luminance-current efficiency characteristics of the lightemitting elements of this embodiment. In FIG. 14, the horizontal axisrepresents luminance (cd/m²) and the vertical axis represents currentefficiency (cd/A). FIG. 15 shows voltage-luminance characteristicsthereof. In FIG. 15, the horizontal axis represents voltage (V) and thevertical axis represents luminance (cd/m²). FIG. 16 showsluminance-external quantum efficiency characteristics thereof. In FIG.16, the horizontal axis represents luminance (cd/m²) and the verticalaxis represents external quantum efficiency (%). Furthermore, Table 2shows the voltage (V), current density (mA/cm²), CIE chromaticitycoordinates (x, y), current efficiency (cd/A), power efficiency (lm/W),and external quantum efficiency (%) of each light-emitting element at aluminance of around 1000 cd/m².

TABLE 2 current current power external voltage density chromaticityluminance efficiency efficiency quantum (V) (mA/cm²) x y (cd/m²) (cd/A)(lm/W) efficiency (%) light-emitting 3.0 1.6 0.43 0.58 1100 67 70 19element 1 comparative 2.9 1.3 0.43 0.56 1000 76 82 22 light-emittingelement 2 comparative 2.9 1.3 0.43 0.56 1000 81 88 23 light-emittingelement 3

As shown in Table 2, as to the light-emitting element 1, the CIEchromaticity coordinates (x, y)=(0.43, 0.56) when the luminance is 1100cd/m². As to the comparative light-emitting element 2, the CIEchromaticity coordinates (x, y)=(0.43, 0.56) when the luminance is 1000cd/m². As to the comparative light-emitting element 3, the CIEchromaticity coordinates (x, y)=(0.43, 0.56) when the luminance is 1000cd/m². These results show that yellow-green light emission originatingfrom [Ir(tBuppm)₂(acac)] is obtained from the light-emitting elements ofthis example.

FIG. 14, FIG. 15, FIG. 16, and Table 2 demonstrate that each of thelight-emitting element 1, the comparative light-emitting element 2, andthe comparative light-emitting element 3 is driven at a low voltage andhas high current efficiency and high external quantum efficiency.

Next, the light-emitting element. 1, the comparative light-emittingelement 2, and the comparative light-emitting element 3 were subjectedto reliability tests. The results of the reliability tests are shown inFIG. 17. In FIG. 17, the vertical axis represents normalized luminance(%) with an initial luminance of 100%, and the horizontal axisrepresents driving time (h) of the elements. In the reliability tests,the light-emitting elements of this example were driven at roomtemperature under the conditions that the initial luminance was set to5000 cd/m² and the current density was constant. FIG. 17 shows that thelight-emitting element 1 keeps its luminance 85% of the initialluminance after the driving for 180 hours. The comparativelight-emitting element 2 keeps its luminance 53% of the initialluminance after the driving for 160 hours. The comparativelight-emitting element 3 keeps its luminance 56% of the initialluminance after the driving for 160 hours. These results of thereliability tests reveal that the light-emitting element 1 has a longerlifetime than the comparative light-emitting elements 2 and 3.

As described above, PCBNBSF synthesized in Example 2 was used for alight-emitting layer; thus, a light-emitting element with a longlifetime was able to be achieved.

Example 4

In this example, a light-emitting element of one embodiment of thepresent invention will be described with reference to FIG. 13. Chemicalformulae of materials used in this example are shown below. Note thatthe structural formulae of the materials described in Example 3 areomitted.

Methods of manufacturing a light-emitting element 4 and a comparativelight-emitting element 5 of this example will be described below.

(Light-Emitting Element 4)

First, the first electrode 1101, the hole-injection layer 1111, and thehole-transport layer 1112 were formed over the glass substrate 1100 inthe same manner as the light-emitting element 1.

Next, the light-emitting layer 1113 was formed over the hole-transportlayer 1112 by co-evaporation of2-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline(abbreviation: 2mDBTBPDBq-II),9,9-dimethyl-N-[4-(1-naphthyl)phenyl]-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9H-fluoren-2-amine(abbreviation: PCBNBF), and(acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium (III)(abbreviation: [Ir(dppm)₂(acac)]). Here, the weight ratio of2mDBTBPDBq-II to PCBNBF to [Ir(dppm)₂(acac)] was adjusted to0.8:0.2:0.05 (=2mDBTBPDBq-II: PCBNBF: [Ir(dppm)₂(acac)]). Thelight-emitting layer 1113 was formed to have a thickness of 40 nm.

Next, over the light-emitting layer 1113, 2mDBTBPDBq-II was deposited toa thickness of 15 nm and then BPhen was deposited to a thickness of 15nm, whereby the electron-transport layer 1114 was formed.

Furthermore, LiF was deposited to a thickness of 1 nm over theelectron-transport layer 1114 by evaporation, whereby theelectron-injection layer 1115 was formed.

Lastly, a film of aluminum was formed to a thickness of 200 nm byevaporation, whereby the second electrode 1103 functioning as a cathodewas formed. Thus, the light-emitting element 4 of this example wasmanufactured.

Note that, in the above evaporation process, evaporation was allperformed by a resistance heating method.

(Comparative Light-Emitting Element 5)

The light-emitting layer 1113 of the comparative light-emitting element5 was formed by co-evaporation of 2mDBTBPDBq-II,4,4′-di(1-naphthyl)-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBNBB), and [Ir(dppm)₂(acac)]. Here, the weight ratio of2mDBTBPDBq-II to PCBNBB to [Ir(dppm)₂(acac)] was adjusted to0.8:0.2:0.05 (=2mDBTBPDBq-II: PCBNBB: [Ir(dppm)₂(acac)]). The thicknessof the light-emitting layer 1113 was set to 40 nm.

The layers other than the light-emitting layer 1113 were formed in thesame manner as the light-emitting element 4.

Table 3 shows the element structures of the light-emitting elements ofthis example, which were manufactured in the above manner.

TABLE 3 first hole injection hole-transport light-emittingelectron-transport etectron injection second electrode layer layer layerlayer layer electrode light-emitting ITSO DBT3P-II:MoOx BPAFLP2mDBTBPDBq-II:PCBNBF: 2mDBT BPhen LiF Al element 4 110 nm (=4:2) 20 nm[Ir(dppm)₂(acac)] BPDBq-II 15 nm 1 nm 200 nm 40 nm (=0.8:0.2:0.05) 40 nm15 nm comparative 2mDBTBPDBq-II:PCBNBB: light-emitting [Ir(dppm)₂(acac)]element 5 (=0.8:0.2:0.05) 40 nm

In a glove box containing a nitrogen atmosphere, each of thelight-emitting element 4 and the comparative light-emitting element 5was sealed with a glass substrate so as not to be exposed to the air.Then, operation characteristics of these light-emitting elements weremeasured. Note that the measurement was carried out at room temperature(in an atmosphere kept at 25° C.).

FIG. 18 shows luminance-current efficiency characteristics of the lightemitting elements of this embodiment. In FIG. 18, the horizontal axisrepresents luminance (cd/m²) and the vertical axis represents currentefficiency (cd/A). FIG. 19 shows voltage-luminance characteristicsthereof. In FIG. 19, the horizontal axis represents voltage (V) and thevertical axis represents luminance (cd/m²). FIG. 20 showsluminance-external quantum efficiency characteristics thereof. In FIG.20, the horizontal axis represents luminance (cd/m²) and the verticalaxis represents external quantum efficiency (%). Furthermore, Table 4shows the voltage (V), current density (mA/cm²), CIE chromaticitycoordinates (x, y), current efficiency (cd/A), power efficiency (lm/W),and external quantum efficiency (%) of each light-emitting element at aluminance of around 1000 cd/m².

TABLE 4 current current power external voltage density chromaticityluminance efficiency efficiency quantum (V) (mA/cm²) x y (cd/m²) (cd/A)(lm/W) efficiency (%) light-emitting 3.0 1.5 0.55 0.45 1000 66 69 25element 4 comparative 3.0 1.4 0.55 0.44 900 63 66 25 light-emittingelement 5

As shown in Table 4, as to the light-emitting element 4, the CIEchromaticity coordinates (x, y)=(0.55, 0.45) when the luminance is 1000cd/m², and as to the comparative light-emitting element 5, the CIEchromaticity coordinates (x, y)=(0.55, 0.44) when the luminance is 900cd/m². These results show that orange light emission originating from[Ir(dppm)₂(acac)] is obtained from the light-emitting elements of thisexample.

As can be seen from FIG. 18, FIG. 19, FIG. 20, and Table 4, each of thelight-emitting element 4 and the comparative light-emitting element 5 isdriven at a low voltage and has high current efficiency and highexternal quantum efficiency.

Next, the light-emitting element 4 and the comparative light-emittingelement 5 were subjected to reliability tests. The results of thereliability tests are shown in FIGS. 21A and 21B. In FIGS. 21A and 21B,the vertical axis represents normalized luminance (%) with an initialluminance of 100%, and the horizontal axis represents driving time (h)of the elements. In the reliability tests, the light-emitting elementsof this example were driven at room temperature under the conditionsthat the initial luminance was set to 5000 cd/m² and the current densitywas constant. FIGS. 21A and 21B show that the light-emitting element 4keeps its luminance 94% of the initial luminance after the driving for370 hours, and the comparative light-emitting element 5 keeps itsluminance 92% of the initial luminance after the driving for 460 hours.These results of the reliability tests reveal that the light-emittingelement 4 has a longer lifetime than the comparative light-emittingelement 5.

As described above, PCBNBF synthesized in Example 1 was used for alight-emitting layer; thus, a light-emitting element with a longlifetime was able to be achieved.

Reference Example

A method of synthesizing4,6-bis[3-(dibenzothiophen-4-yl)phenyl]pyrimidine (abbreviation:4,6mDBTP2Pm-II) used in Example 4 will be described.

Synthesis Scheme (x-1) of 4,6mDBTP2Pm-II is shown.

Into a 100-mL recovery flask were put 1.0 g (6.7 mmol) of4,6-dichloropyrimidine, 5.1 g (17 mmol) of3-(dibenzothiophen-4-yl)-phenylboronic acid, 3.5 g (34 mmol) of sodiumcarbonate, 20 mL of 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone(abbreviation: DMPU), and 10 mL of water. This mixture was degassed bybeing stirred while the pressure was reduced. To this mixture was added56 mg (81 μmol) of bis(triphenylphosphine)palladium(II) dichloride, andthe atmosphere was replaced with argon. The mixture was stirred whilethe reaction container was heated by irradiation with microwaves (2.45GHz, 100 W) for 1.5 hours. After the heating, water was added to themixture, and the mixture was filtered to give a residue. The obtainedsolid was washed with dichloromethane and ethanol. To the obtained solidwas added toluene, and the mixture was subjected to suction filtrationthrough Celite, alumina, and Florisil. The filtrate was concentrated togive a solid. The obtained solid was recrystallized from toluene to give2.5 g of a white solid in a yield of 63%.

By a train sublimation method, 2.5 g of the obtained solid was purified.The purification by sublimation was performed by heating at 300° C.under a pressure of 3.6 Pa with a flow rate of argon gas of 5 mL/min.After the purification by sublimation, 2.0 g of a white solid wasobtained at a collection rate of 79%.

This compound was identified as4,6-bis[3-(dibenzothiophen-4-yl)phenyl]pyrimidine (abbreviation:4,6mDBTP2Pm-II), which was an objective substance, by a nuclear magneticresonance (NMR) method.

¹H NMR data of the obtained substance are as follows: ¹H NMR (CDCl₃, 300MHz): δ=7.41-7.51 (m, 4H), 7.58-7.62 (m, 4H), 7.68-7.79 (m, 4H), 8.73(dt, J1=8.4 Hz, J2=0.9 Hz, 2H), 8.18-8.27 (m, 7H), 8.54 (t, J1=1.5 Hz,2H), 9.39 (d, J1=0.9 Hz, 1H).

This application is based on Japanese Patent Application serial no.2012-172952 filed with Japan Patent Office on Aug. 3, 2012, the entirecontents of which are hereby incorporated by reference.

What is claimed is:
 1. An organic compound represented by GeneralFormula (G0),

wherein Ar¹ represents a naphthyl group, wherein Ar² represents acarbazolyl group, wherein Ar³ represents a fluorenyl group or aspirofluorenyl group, wherein α¹ and α² each independently represent aphenylene group or a biphenyldiyl group, wherein the naphthyl group, thecarbazolyl group, the fluorenyl group, the spirofluorenyl group, thephenylene group, and the biphenyldiyl group are each independentlyunsubstituted or substituted with a substituent, and wherein thesubstituent is an alkyl group having 1 to 10 carbon atoms or an arylgroup having 6 to 25 carbon atoms.
 2. The organic compound according toclaim 1, wherein Ar² is one selected from the group consisting ofStructural Formulae (1-1) to (1-27).


3. The organic compound according to claim 1, wherein Ar¹ is oneselected from the group consisting of Structural Formulae (2-1) to(2-3).


4. The organic compound according to claim 1, wherein α¹ is one selectedfrom the group consisting of Structural Formulae (3-1) to (3-12).


5. The organic compound according to claim 1, wherein α² is one selectedfrom the group consisting of Structural Formulae (3-1) to (3-12).


6. The organic compound according to claim 1, wherein Ar³ is oneselected from the group consisting of Structural Formulae (4-1) to(4-5).


7. An organic compound represented by General Formula (G1),

wherein Ar¹ represents a naphthyl group, wherein Ar³ represents afluorenyl group or a spirofluorenyl group, wherein Ar⁴ represents anaryl group having 6 to 25 carbon atoms, wherein α¹ represents aphenylene group or a biphenyldiyl group, wherein R¹¹ to R¹⁷ and R²¹ toR²⁴ each independently represent hydrogen, an alkyl group having 1 to 10carbon atoms, or an aryl group having 6 to 25 carbon atoms, wherein thenaphthyl group, the fluorenyl group, the spirofluorenyl group, thephenylene group, and the biphenyldiyl group are each independentlyunsubstituted or substituted with a substituent, and wherein thesubstituent is an alkyl group having 1 to 10 carbon atoms or an arylgroup having 6 to 25 carbon atoms.
 8. The organic compound according toclaim 7, wherein Ar² is one selected from the group consisting ofStructural Formulae (1-1) to (1-27).


9. The organic compound according to claim 7, wherein Ar¹ is oneselected from the group consisting of Structural Formulae (2-1) to(2-3).


10. The organic compound according to claim 7, wherein α¹ is oneselected from the group consisting of Structural Formulae (3-1) to(3-12).


11. The organic compound according to claim 7, wherein Ar³ is oneselected from the group consisting of Structural Formulae (4-1) to(4-5).


12. An organic compound represented by General Formula (G2)

and wherein Ar¹ represents a naphthyl group, wherein Ar³ represents afluorenyl group or a spirofluorenyl group, wherein α¹ represents aphenylene group or a biphenyldiyl group, wherein R¹¹ to R¹⁷ and R²¹ toR²⁴ each independently represent hydrogen, an alkyl group having 1 to 10carbon atoms, or an aryl group having 6 to 25 carbon atoms, wherein R³¹to R³⁵ each independently represent hydrogen or an alkyl group having 1to 10 carbon atoms, wherein the naphthyl group, the fluorenyl group, thespirofluorenyl group, the phenylene group, and the biphenyldiyl groupare each independently unsubstituted or substituted with a substituent,and wherein the substituent is an alkyl group having 1 to 10 carbonatoms or an aryl group having 6 to 25 carbon atoms.
 13. The organiccompound according to claim 12, wherein Ar¹ is one selected from thegroup consisting of Structural Formulae (2-1) to (2-3).


14. The organic compound according to claim 12, wherein α¹ is oneselected from the group consisting of Structural Formulae (3-1) to(3-12).


15. The organic compound according to claim 12, wherein Ar³ is oneselected from the group consisting of Structural Formulae (4-1) to(4-5).


16. The organic compound according to claim 12, wherein the organiccompound is represented by General Formula (G3)

wherein R⁴¹ to R⁴⁷ and R⁵¹ to R⁵⁴ each independently represent hydrogen,an alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to25 carbon atoms, and wherein R³¹ to R³⁵ each independently representhydrogen or an alkyl group having 1 to 10 carbon atoms.